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1196 lines
22 KiB
Markdown
1196 lines
22 KiB
Markdown
Nix 备忘清单
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===
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Nix 快速参考备忘单，旨在帮助编写基础的 Nix 代码。Nix 是一个纯函数式包管理器和 NixOS 系统的基础语言。
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类型与语法
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---
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### 字符串
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<!--rehype:wrap-class=row-span-2-->
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```nix
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let
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x = "单行字符串";
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y = ''
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多行字符串
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支持换行和缩进
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'';
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z = ''
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前导空格会被自动处理
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这行会保持缩进
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'';
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in
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```
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#### 字符串插值
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```nix
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let
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name = "世界";
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greeting = "你好，${name}！";
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in
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```
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#### 转义字符
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```nix
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let
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escaped = ''
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引号：\"hello\"，换行：\n，制表符：\t
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'';
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in
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```
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### 整数
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```nix
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let
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x = -123;
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y = 123;
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# 支持不同进制
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hex = 0xFF; # 十六进制: 255
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bin = 0b1010; # 二进制: 10
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oct = 0o755; # 八进制: 493
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in
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```
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### 浮点数
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```nix
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let
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x = -0.32;
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y = 0.45;
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scientific = 1.23e-4; # 科学记数法
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inf = 1.0 / 0.0; # 无穷大
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in
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```
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### 布尔值
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```nix
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let
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x = true;
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y = false;
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# 布尔运算
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and_result = true && false; # false
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or_result = true || false; # true
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not_result = !true; # false
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in
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```
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### 空值
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```nix
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let
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x = null;
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# null 表示缺失值
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# 类似于其他语言的 None 或 undefined
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in
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```
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### 路径
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```nix
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let
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absolute = /usr/bin/env; # 绝对路径
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relative = ./config.nix; # 相对路径
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home = ~/Documents; # 家目录路径
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# 路径会在构建时自动复制到 Nix store
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in
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```
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### 属性集
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<!--rehype:wrap-class=row-span-2-->
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```nix
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let
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x = {
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name = "张三";
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age = 25;
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address = {
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city = "北京";
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district = "朝阳区";
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};
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};
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y = { c = 3; };
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# 递归属性集
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rec_set = rec {
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x = 1;
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y = x + 1; # 可以引用同级属性
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};
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in
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```
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参见 [属性集操作](#属性集)
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### 列表
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<!--rehype:wrap-class=row-span-2-->
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```nix
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let
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numbers = [ 1 2 3 4 5 ];
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mixed = [
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1
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"这是字符串"
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23.0
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null
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{ name = "属性集"; }
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];
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# 列表可以包含任意类型的元素
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nested = [ [ 1 2 ] [ 3 4 ] ];
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in
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```
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### 注释
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#### ↓ 单行注释
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```nix
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# 这是单行注释
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let x = 1; in x # 行末注释
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```
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#### ↓ 多行注释
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```nix
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/*
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这是多行注释
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可以跨越多行
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/* 可以嵌套 */
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*/
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```
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作用域管理
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---
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### 定义局部变量
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<!--rehype:wrap-class=row-span-2-->
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```nix
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let
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x = 1;
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y = 2;
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z = x + y; # 可以引用前面定义的变量
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in
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x + y + z # 返回 6
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```
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#### 嵌套 let 表达式
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```nix
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let
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outer = 10;
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in
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let
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inner = 5;
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in
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outer + inner # 返回 15
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```
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### 将变量添加到作用域
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```nix
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let
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x = 1;
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y = 2;
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in
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{ inherit x y; } # 继承多个变量
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```
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#### ↓ 等价于
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```nix
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let
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x = 1;
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y = 2;
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in
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{ x = x; y = y; }
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```
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### 从属性集继承属性
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<!--rehype:wrap-class=row-span-2-->
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```nix
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let
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config = {
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host = "localhost";
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port = 8080;
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ssl = true;
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};
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in
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{
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inherit (config) host port;
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# 只继承特定属性
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}
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```
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#### ↓ 等价于
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```nix
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let
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config = {
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host = "localhost";
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port = 8080;
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ssl = true;
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};
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in
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{
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host = config.host;
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port = config.port;
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}
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```
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### 将所有属性引入作用域
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```nix
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let
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config = {
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host = "localhost";
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port = 8080;
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database = "myapp";
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};
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in
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with config;
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"${host}:${toString port}/${database}" # 返回 "localhost:8080/myapp"
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```
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#### 注意事项
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```nix
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let
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x = 1;
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attrs = { x = 2; y = 3; };
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in
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with attrs;
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x + y # x = 1 (局部变量优先级更高), y = 3
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```
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条件表达式
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---
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### 基本条件表达式
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<!--rehype:wrap-class=row-span-2-->
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```nix
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let
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x = 10;
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result = if x > 0
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then "正数"
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else if x < 0
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then "负数"
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else "零";
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in
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result
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```
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#### 布尔条件判断
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```nix
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let
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isEnabled = true;
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config = if isEnabled
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then { port = 8080; debug = true; }
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else { port = 80; debug = false; };
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in
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config
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```
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#### 字符串条件判断
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```nix
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let
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env = "production";
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database = if env == "production"
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then "prod-db.example.com"
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else if env == "staging"
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then "staging-db.example.com"
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else "localhost";
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in
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database
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```
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### 复杂条件判断
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<!--rehype:wrap-class=col-span-2-->
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```nix
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let
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user = { name = "张三"; age = 25; isAdmin = true; };
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message = if user.isAdmin && user.age >= 18
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then "管理员用户: ${user.name}"
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else "普通用户: ${user.name}";
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in
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message
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```
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### 条件表达式中的属性集
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<!--rehype:wrap-class=col-span-2-->
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```nix
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let
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env = "production";
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config = if env == "development"
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then {
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debug = true;
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logLevel = "debug";
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database.host = "localhost";
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}
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else {
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debug = false;
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logLevel = "info";
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database.host = "prod-db.example.com";
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};
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in
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config
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```
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属性集
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---
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### 定义属性集
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```nix
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let
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person = {
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name = "李四";
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age = 30;
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skills = [ "编程" "设计" "管理" ];
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contact = {
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email = "lisi@example.com";
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phone = "138-0000-0000";
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};
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};
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in
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person
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```
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### 动态属性名
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```nix
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let
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key = "dynamicKey";
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attrs = {
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${key} = "动态值";
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"static-key" = "静态值";
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};
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in
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attrs # { dynamicKey = "动态值"; static-key = "静态值"; }
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```
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### 更新属性集
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```nix
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let
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base = { x = 1; y = 2; };
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updated = base // { y = 3; z = 4; }; # 合并属性集
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in
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updated # { x = 1; y = 3; z = 4; }
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```
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#### 深度合并
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```nix
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let
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config1 = {
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server = { host = "localhost"; port = 8080; };
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database = { name = "test"; };
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};
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config2 = {
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server = { port = 9000; ssl = true; };
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cache = { enabled = true; };
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};
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# 注意：// 操作符只进行浅合并
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merged = config1 // config2;
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# server 属性会被完全替换，而不是深度合并
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in
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merged
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```
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### 检查属性是否存在
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```nix
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let
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person = { name = "王五"; age = 28; };
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in
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{
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hasName = person ? name; # true
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hasEmail = person ? email; # false
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hasNested = person ? contact.email; # false (嵌套检查)
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}
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```
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### 访问属性
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```nix
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let
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config = {
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server = {
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host = "localhost";
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port = 8080;
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};
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};
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in
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{
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host = config.server.host; # 访问嵌套属性
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port = config.server.port;
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}
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```
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#### 可选属性访问
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```nix
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let
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config = { server = { host = "localhost"; }; };
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in
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{
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port = config.server.port or 3000; # 如果不存在则使用默认值
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timeout = config.timeout or 30; # 30
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ssl = config.server.ssl or false; # false
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}
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```
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连接与插值
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---
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### 连接列表
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```nix
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let
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list1 = [ 1 2 3 ];
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list2 = [ 4 5 6 ];
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combined = list1 ++ list2; # [ 1 2 3 4 5 6 ]
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# 多个列表连接
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all = [ 0 ] ++ list1 ++ list2 ++ [ 7 8 ];
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in
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all # [ 0 1 2 3 4 5 6 7 8 ]
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```
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### 连接路径与字符串
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```nix
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let
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base = /usr/bin;
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executable = base + /python3; # /usr/bin/python3
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# 路径与字符串连接
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config_path = /etc + "/nginx/nginx.conf"; # /etc/nginx/nginx.conf
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# 字符串连接
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greeting = "你好" + "，世界！"; # "你好，世界！"
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in
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{ inherit executable config_path greeting; }
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```
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### 字符串插值
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```nix
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let
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name = "张三";
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age = 25;
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score = 95.5;
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in
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{
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greeting = "你好，${name}！";
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info = "姓名：${name}，年龄：${toString age}";
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result = "考试成绩：${toString score}分";
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# 复杂表达式插值
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status = "用户 ${name} ${if age >= 18 then "已成年" else "未成年"}";
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# 路径插值
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config_file = "${./configs}/${name}.conf";
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}
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```
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函数
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---
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### 简单函数
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```nix
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let
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# 单参数函数
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increment = x: x + 1;
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double = x: x * 2;
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# 使用函数
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result1 = increment 5; # 6
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result2 = double 3; # 6
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in
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{ inherit result1 result2; }
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```
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### 命名参数
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<!--rehype:wrap-class=col-span-2 row-span-4-->
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```nix
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let
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# 基本命名参数
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createUser = {name, age, email}: {
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inherit name age email;
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id = builtins.hashString "md5" email;
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};
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user = createUser {
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name = "张三";
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age = 25;
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email = "zhangsan@example.com";
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};
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in
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user
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```
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#### 忽略额外参数
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```nix
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let
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# 使用 ... 忽略额外的参数
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processConfig = {host, port, ...}: {
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url = "${host}:${toString port}";
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};
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result = processConfig {
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host = "localhost";
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port = 8080;
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ssl = true; # 会被忽略
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timeout = 30; # 会被忽略
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};
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in
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result # { url = "localhost:8080"; }
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```
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#### 默认参数值
|
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```nix
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let
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# 为参数提供默认值
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createServer = {
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host ? "localhost",
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port ? 8080,
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ssl ? false
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}: {
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inherit host port ssl;
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url =
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let proto = if ssl then "https" else "http";
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in "${proto}://${host}:${toString port}";
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};
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# 使用所有默认值
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server1 = createServer {};
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# 只覆盖 port
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server2 = createServer {port = 3000;};
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# 覆盖多个参数
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server3 = createServer {
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host = "example.com";
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port = 443;
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ssl = true;
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};
|
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in
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{ inherit server1 server2 server3; }
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```
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|
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#### 绑定到变量
|
||
|
||
```nix
|
||
let
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||
# 将整个参数集绑定到变量，同时解构部分参数
|
||
logMessage = {
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level,
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message,
|
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timestamp ? null
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}@args: {
|
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formatted = "[${level}] ${message}";
|
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raw = args; # 保留原始参数集
|
||
hasTimestamp =
|
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args ? timestamp && timestamp != null;
|
||
};
|
||
|
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log = logMessage {
|
||
level = "INFO";
|
||
message = "服务器启动成功";
|
||
user = "admin"; # 额外参数也会保存在 args 中
|
||
};
|
||
in
|
||
log
|
||
```
|
||
|
||
### 多参数函数
|
||
|
||
```nix
|
||
let
|
||
# 柯里化函数
|
||
add = x: y: x + y;
|
||
multiply = x: y: z: x * y * z;
|
||
|
||
# 部分应用
|
||
add10 = add 10; # 等价于 y: 10 + y
|
||
|
||
# 使用示例
|
||
result1 = add 3 4; # 7
|
||
result2 = add10 5; # 15
|
||
result3 = multiply 2 3 4; # 24
|
||
in
|
||
{ inherit result1 result2 result3; }
|
||
```
|
||
|
||
### 高阶函数
|
||
|
||
```nix
|
||
let
|
||
# 接受函数作为参数的高阶函数
|
||
applyTwice = f: x: f (f x);
|
||
|
||
# 返回函数的高阶函数
|
||
createMultiplier = factor: x: x * factor;
|
||
|
||
# 函数组合
|
||
compose = f: g: x: f (g x);
|
||
|
||
# 使用示例
|
||
double = x: x * 2;
|
||
increment = x: x + 1;
|
||
|
||
result1 = applyTwice double 3; # 12
|
||
triple = createMultiplier 3;
|
||
result2 = triple 5; # 15
|
||
doubleAndIncrement =
|
||
compose increment double;
|
||
result3 = doubleAndIncrement 4; # 9
|
||
in
|
||
{ inherit result1 result2 result3; }
|
||
```
|
||
|
||
### 递归函数
|
||
|
||
```nix
|
||
let
|
||
# 计算阶乘
|
||
factorial = n:
|
||
if n <= 1
|
||
then 1
|
||
else n * factorial (n - 1);
|
||
|
||
# 斐波那契数列
|
||
fibonacci = n:
|
||
if n <= 1
|
||
then n
|
||
else fibonacci (n - 1) + fibonacci (n - 2);
|
||
|
||
# 列表长度计算
|
||
listLength = list:
|
||
if list == []
|
||
then 0
|
||
else 1 + listLength (builtins.tail list);
|
||
|
||
# 使用示例
|
||
fact5 = factorial 5; # 120
|
||
fib7 = fibonacci 7; # 13
|
||
len = listLength [1 2 3 4]; # 4
|
||
in
|
||
{ inherit fact5 fib7 len; }
|
||
```
|
||
|
||
### 条件函数
|
||
|
||
```nix
|
||
let
|
||
```nix
|
||
let
|
||
# 根据条件选择不同的处理函数
|
||
processData = condition: data:
|
||
let
|
||
uppercaseProcessor = str:
|
||
builtins.replaceStrings
|
||
["a" "e" "i" "o" "u"]
|
||
["A" "E" "I" "O" "U"] str;
|
||
|
||
lengthProcessor = str:
|
||
toString (builtins.stringLength str);
|
||
|
||
reverseProcessor = str:
|
||
let
|
||
len = builtins.stringLength str;
|
||
chars = builtins.genList
|
||
(i: builtins.substring
|
||
(len - 1 - i) 1 str) len;
|
||
in
|
||
builtins.concatStringsSep "" chars;
|
||
in
|
||
if condition == "uppercase"
|
||
then uppercaseProcessor data
|
||
else if condition == "length"
|
||
then lengthProcessor data
|
||
else if condition == "reverse"
|
||
then reverseProcessor data
|
||
else data;
|
||
|
||
# 使用示例
|
||
text = "hello world";
|
||
result1 = processData "uppercase" text;
|
||
result2 = processData "length" text;
|
||
result3 = processData "reverse" text;
|
||
in
|
||
{ inherit result1 result2 result3; }
|
||
```
|
||
|
||
### 函数工厂
|
||
|
||
```nix
|
||
let
|
||
# 创建验证器函数的工厂
|
||
createValidator = rules: value:
|
||
let
|
||
checkRule = rule:
|
||
if rule.type == "minLength"
|
||
then
|
||
builtins.stringLength value >= rule.value
|
||
else if rule.type == "maxLength"
|
||
then
|
||
builtins.stringLength value <= rule.value
|
||
else if rule.type == "contains"
|
||
then
|
||
builtins.match ".*${rule.value}.*" value
|
||
!= null
|
||
else true;
|
||
|
||
results = map checkRule rules;
|
||
allValid = builtins.all (x: x) results;
|
||
in
|
||
{
|
||
valid = allValid;
|
||
value = value;
|
||
errors = builtins.filter
|
||
(rule: !checkRule rule) rules;
|
||
};
|
||
|
||
# 创建特定的验证器
|
||
emailValidator = createValidator [
|
||
{ type = "minLength"; value = 5; }
|
||
{ type = "contains"; value = "@"; }
|
||
{ type = "contains"; value = "."; }
|
||
];
|
||
|
||
passwordValidator = createValidator [
|
||
{ type = "minLength"; value = 8; }
|
||
{ type = "maxLength"; value = 32; }
|
||
];
|
||
|
||
# 使用示例
|
||
email_result = emailValidator "user@example.com";
|
||
password_result = passwordValidator "mypassword123";
|
||
in
|
||
{ inherit email_result password_result; }
|
||
```
|
||
|
||
### 函数式编程工具
|
||
|
||
```nix
|
||
let
|
||
# 映射函数
|
||
mapList = f: list:
|
||
if list == []
|
||
then []
|
||
else
|
||
let head = f (builtins.head list);
|
||
tail = mapList f (builtins.tail list);
|
||
in [ head ] ++ tail;
|
||
|
||
# 过滤函数
|
||
filterList = predicate: list:
|
||
if list == []
|
||
then []
|
||
else
|
||
let
|
||
head = builtins.head list;
|
||
tail = builtins.tail list;
|
||
filtered_tail =
|
||
filterList predicate tail;
|
||
in
|
||
if predicate head
|
||
then [ head ] ++ filtered_tail
|
||
else filtered_tail;
|
||
|
||
# 归约函数
|
||
reduceList = f: initial: list:
|
||
if list == []
|
||
then initial
|
||
else
|
||
let head = builtins.head list;
|
||
tail = builtins.tail list;
|
||
in reduceList f (f initial head) tail;
|
||
|
||
# 使用示例
|
||
numbers = [ 1 2 3 4 5 ];
|
||
doubled = mapList (x: x * 2) numbers;
|
||
evens = filterList (x: x mod 2 == 0) numbers;
|
||
sum = reduceList (acc: x: acc + x) 0 numbers;
|
||
product = reduceList (acc: x: acc * x) 1 numbers;
|
||
in
|
||
{ inherit doubled evens sum product; }
|
||
```
|
||
|
||
内置函数
|
||
---
|
||
|
||
### 类型检查函数
|
||
|
||
```nix
|
||
let
|
||
value = "hello";
|
||
in
|
||
{
|
||
isString = builtins.isString value;
|
||
# true
|
||
isInt = builtins.isInt value;
|
||
# false
|
||
isBool = builtins.isBool true;
|
||
# true
|
||
isList = builtins.isList [1 2 3];
|
||
# true
|
||
isAttrs = builtins.isAttrs {x = 1;};
|
||
# true
|
||
isFunction = builtins.isFunction (x: x);
|
||
# true
|
||
}
|
||
```
|
||
|
||
### 字符串操作函数
|
||
<!--rehype:wrap-class=col-span-2-->
|
||
|
||
```nix
|
||
let
|
||
text = "Hello, Nix World!";
|
||
in
|
||
{
|
||
length = builtins.stringLength text; # 18
|
||
substring = builtins.substring 7 3 text; # "Nix"
|
||
split = builtins.split " " text; # 分割字符串
|
||
replace = builtins.replaceStrings ["Nix"] ["世界"] text; # "Hello, 世界 World!"
|
||
|
||
# 大小写转换需要自定义实现
|
||
toLower = builtins.replaceStrings
|
||
["A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M"
|
||
"N" "O" "P" "Q" "R" "S" "T" "U" "V" "W" "X" "Y" "Z"]
|
||
["a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m"
|
||
"n" "o" "p" "q" "r" "s" "t" "u" "v" "w" "x" "y" "z"]
|
||
"HELLO";
|
||
}
|
||
```
|
||
|
||
### 列表操作函数
|
||
|
||
```nix
|
||
let
|
||
numbers = [1 2 3 4 5];
|
||
strings = ["apple" "banana" "cherry"];
|
||
in
|
||
{
|
||
length = builtins.length numbers; # 5
|
||
head = builtins.head numbers; # 1
|
||
tail = builtins.tail numbers; # [2 3 4 5]
|
||
|
||
# 映射函数
|
||
doubled = map (x: x * 2) numbers; # [2 4 6 8 10]
|
||
# 过滤函数
|
||
evens = builtins.filter (x: x mod 2 == 0) numbers; # [2 4]
|
||
# 折叠函数
|
||
sum = builtins.foldl' (acc: x: acc + x) 0 numbers; # 15
|
||
# 元素查找
|
||
hasThree = builtins.elem 3 numbers; # true
|
||
# 排序
|
||
sorted = builtins.sort (a: b: a < b) [3 1 4 1 5 9]; # [1 1 3 4 5 9]
|
||
}
|
||
```
|
||
|
||
### 属性集操作函数
|
||
<!--rehype:wrap-class=col-span-2-->
|
||
|
||
```nix
|
||
let
|
||
attrs = { a = 1; b = 2; c = 3; };
|
||
in
|
||
{
|
||
keys = builtins.attrNames attrs; # ["a" "b" "c"]
|
||
values = builtins.attrValues attrs; # [1 2 3]
|
||
hasAttr = builtins.hasAttr "b" attrs; # true
|
||
|
||
# 映射属性值
|
||
doubled = builtins.mapAttrs (name: value: value * 2) attrs;
|
||
# { a = 2; b = 4; c = 6; }
|
||
|
||
# 过滤属性
|
||
filtered = builtins.filterAttrs (name: value: value > 1) attrs;
|
||
# { b = 2; c = 3; }
|
||
|
||
# 移除属性
|
||
removed = builtins.removeAttrs attrs ["b"]; # { a = 1; c = 3; }
|
||
}
|
||
```
|
||
|
||
导入与模块
|
||
---
|
||
|
||
### 导入文件
|
||
|
||
```nix
|
||
let
|
||
# 导入其他 Nix 文件
|
||
utils = import ./utils.nix;
|
||
config = import ./config.nix;
|
||
|
||
# 带参数导入
|
||
lib = import <nixpkgs/lib>;
|
||
|
||
# 导入并传递参数
|
||
myModule = import ./module.nix {
|
||
pkgs = import <nixpkgs> {};
|
||
config = { enableFeature = true; };
|
||
};
|
||
in
|
||
{
|
||
inherit utils config lib myModule;
|
||
}
|
||
```
|
||
|
||
### 模块定义
|
||
<!--rehype:wrap-class=col-span-2-->
|
||
|
||
```nix
|
||
# module.nix 示例
|
||
{ pkgs, config, ... }:
|
||
|
||
{
|
||
# 模块选项
|
||
options = {
|
||
services.myapp = {
|
||
enable = lib.mkOption {
|
||
type = lib.types.bool;
|
||
default = false;
|
||
description = "启用 MyApp 服务";
|
||
};
|
||
|
||
port = lib.mkOption {
|
||
type = lib.types.int;
|
||
default = 8080;
|
||
description = "MyApp 监听端口";
|
||
};
|
||
};
|
||
};
|
||
|
||
# 模块配置
|
||
config = lib.mkIf config.services.myapp.enable {
|
||
systemd.services.myapp = {
|
||
description = "MyApp 服务";
|
||
after = ["network.target"];
|
||
serviceConfig = {
|
||
ExecStart = "${pkgs.myapp}/bin/myapp --port ${toString config.services.myapp.port}";
|
||
Restart = "always";
|
||
};
|
||
};
|
||
};
|
||
}
|
||
```
|
||
|
||
包管理
|
||
---
|
||
|
||
### 基本包定义
|
||
|
||
```nix
|
||
# default.nix 或 shell.nix
|
||
{ pkgs ? import <nixpkgs> {} }:
|
||
|
||
pkgs.stdenv.mkDerivation {
|
||
pname = "my-app";
|
||
version = "1.0.0";
|
||
|
||
src = ./.; # 当前目录作为源码
|
||
|
||
buildInputs = with pkgs; [
|
||
nodejs
|
||
yarn
|
||
];
|
||
|
||
buildPhase = ''
|
||
yarn install
|
||
yarn build
|
||
'';
|
||
|
||
installPhase = ''
|
||
mkdir -p $out/bin
|
||
cp -r dist/* $out/
|
||
makeWrapper ${pkgs.nodejs}/bin/node $out/bin/my-app \
|
||
--add-flags "$out/index.js"
|
||
'';
|
||
|
||
meta = with pkgs.lib; {
|
||
description = "我的应用程序";
|
||
homepage = "https://example.com";
|
||
license = licenses.mit;
|
||
maintainers = with maintainers; [ "your-name" ];
|
||
};
|
||
}
|
||
```
|
||
|
||
### 开发环境
|
||
<!--rehype:wrap-class=col-span-2-->
|
||
|
||
```nix
|
||
# shell.nix
|
||
{ pkgs ? import <nixpkgs> {} }:
|
||
|
||
pkgs.mkShell {
|
||
buildInputs = with pkgs; [
|
||
# 开发工具
|
||
git
|
||
nodejs
|
||
yarn
|
||
python3
|
||
|
||
# 系统库
|
||
pkg-config
|
||
openssl
|
||
|
||
# 数据库
|
||
postgresql
|
||
redis
|
||
];
|
||
|
||
# 环境变量
|
||
shellHook = ''
|
||
echo "欢迎进入开发环境！"
|
||
export DATABASE_URL="postgresql://localhost/myapp"
|
||
export REDIS_URL="redis://localhost:6379"
|
||
|
||
# 自动启动服务
|
||
if ! pgrep -f "postgres" > /dev/null; then
|
||
echo "启动 PostgreSQL..."
|
||
postgres -D $HOME/postgres-data &
|
||
fi
|
||
'';
|
||
}
|
||
```
|
||
|
||
常用工具函数
|
||
---
|
||
|
||
### 递归函数
|
||
<!--rehype:wrap-class=col-span-2-->
|
||
|
||
```nix
|
||
let
|
||
# 计算阶乘
|
||
factorial = n:
|
||
if n <= 1
|
||
then 1
|
||
else n * factorial (n - 1);
|
||
|
||
# 列表求和
|
||
sumList = list:
|
||
if list == []
|
||
then 0
|
||
else builtins.head list + sumList (builtins.tail list);
|
||
|
||
# 深度合并属性集
|
||
deepMerge = a: b:
|
||
let
|
||
mergeAttr = name:
|
||
let
|
||
aVal = a.${name};
|
||
bVal = b.${name};
|
||
in
|
||
if builtins.isAttrs aVal && builtins.isAttrs bVal
|
||
then deepMerge aVal bVal
|
||
else bVal;
|
||
in
|
||
a // b // builtins.listToAttrs (
|
||
map (name: { inherit name; value = mergeAttr name; })
|
||
(builtins.filter (name: builtins.hasAttr name a) (builtins.attrNames b))
|
||
);
|
||
in
|
||
{
|
||
fact5 = factorial 5; # 120
|
||
listSum = sumList [1 2 3 4 5]; # 15
|
||
merged = deepMerge
|
||
{ a = { x = 1; y = 2; }; c = 3; }
|
||
{ a = { y = 9; z = 4; }; d = 5; };
|
||
}
|
||
```
|
||
|
||
错误处理
|
||
---
|
||
|
||
### 断言
|
||
|
||
```nix
|
||
let
|
||
version = "1.2.3";
|
||
|
||
# 基本断言
|
||
validVersion = assert builtins.stringLength version > 0; version;
|
||
|
||
# 带消息的断言（通过 throw 实现）
|
||
checkPort = port:
|
||
if port < 1 || port > 65535
|
||
then throw "端口号必须在 1-65535 之间，当前值: ${toString port}"
|
||
else port;
|
||
|
||
# 条件检查
|
||
config = {
|
||
port = checkPort 8080;
|
||
host = if builtins.getEnv "HOST" != ""
|
||
then builtins.getEnv "HOST"
|
||
else "localhost";
|
||
};
|
||
in
|
||
config
|
||
```
|
||
|
||
### 异常处理
|
||
<!--rehype:wrap-class=col-span-2-->
|
||
|
||
```nix
|
||
let
|
||
# 安全的属性访问
|
||
safeGet = attrs: path: default:
|
||
let
|
||
keys = builtins.split "\\." path;
|
||
getValue = obj: keyList:
|
||
if keyList == [] then obj
|
||
else if !builtins.isAttrs obj then default
|
||
else if !builtins.hasAttr (builtins.head keyList) obj then default
|
||
else getValue (obj.${builtins.head keyList}) (builtins.tail keyList);
|
||
in
|
||
getValue attrs keys;
|
||
|
||
config = {
|
||
database = {
|
||
host = "localhost";
|
||
port = 5432;
|
||
};
|
||
};
|
||
|
||
# 安全访问嵌套属性
|
||
dbHost = safeGet config "database.host" "default-host"; # "localhost"
|
||
dbUser = safeGet config "database.user" "default-user"; # "default-user"
|
||
in
|
||
{ inherit dbHost dbUser; }
|
||
```
|
||
|
||
来源
|
||
---
|
||
|
||
- [Nix 手册](https://nixos.org/manual/nix/stable/) - 官方用户手册
|
||
- [NixOS 手册](https://nixos.org/manual/nixos/stable/) - NixOS 系统配置指南
|
||
- [Nixpkgs 手册](https://nixos.org/manual/nixpkgs/stable/) - 包管理指南
|
||
- [NixOS/nixpkgs](https://github.com/NixOS/nixpkgs) - 官方包仓库
|
||
- [NixOS/nix](https://github.com/NixOS/nix) - Nix 包管理器源码
|
||
- [Nix Pills](https://nixos.org/guides/nix-pills/) - 深入学习 Nix 的教程
|
||
- [nix-shell](https://nixos.org/manual/nix/stable/command-ref/nix-shell.html) - 创建开发环境
|
||
- [nix-build](https://nixos.org/manual/nix/stable/command-ref/nix-build.html) - 构建包
|
||
- [nix-env](https://nixos.org/manual/nix/stable/command-ref/nix-env.html) - 用户环境管理
|
||
- [nixos-rebuild](https://nixos.org/manual/nixos/stable/administration/administration.html) - 系统重构建
|
||
- [NixOS/marketing](https://github.com/nixos/marketing) _(github.com)_
|
||
- [Nix 语言官方文档](https://nixos.org/manual/nix/stable/expressions/language-values.html) _(nixos.org)_
|