字段默认值
无需重复代码即可初始化字段。
字段默认值 是 CoddyKit 上的免费 Zig Academy 课时。 这是第 3 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Zig Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Zig Academy 课程共包含 4 节课。
本课时的部分内容尚未翻译，以英文显示。
Repeating Yourself
If most instances start the same way, retyping every field is tedious. Zig lets a field carry a default value built into the type.
Give a Field a Default
Add = value after the field type. Any instance that omits that field gets the default automatically.
const Config = struct {
retries: u8 = 3,
};Omit It on Creation
Now you can build a value without mentioning the defaulted field, and it still gets 3.
const c = Config{};Override When You Want
The default is only a starting point. Set the field explicitly in the initializer to use a different value.
const c = Config{ .retries = 5 };Mix Defaults and Required
A struct can blend both. Fields with no default are required; defaulted ones may be skipped.
const User = struct {
name: []const u8,
active: bool = true,
};Empty Initializer
If every field has a default, you can construct with a bare .{} and let all defaults apply at once.
const Settings = struct {
volume: u8 = 50,
muted: bool = false,
};
const s = Settings{};Defaults Are Compile-Time
A default must be a value Zig can compute at compile time, like a literal or a comptime expression.
const Limits = struct {
max: usize = 1024,
};Any Type Can Default
Defaults work for any field type: numbers, bools, slices, even nested structs with their own defaults.
const Box = struct {
size: Settings = Settings{},
};Default to null
An optional field often defaults to null, a clean way to say it starts empty until you fill it in.
const Node = struct {
next: ?*Node = null,
};Cleaner, Safer Code
Defaults shrink your call sites and document intended starting state, so readers see the normal value right in the type.
Defaults Are Per Instance
Each new instance gets its own fresh copy of the default. They never share state between values.
Quick Check
What happens to a defaulted field you leave out?
Recap
You learned default field values: write = value after a field, then omit it to use the default or set it to override. ⚙️
常见问题解答
「字段默认值」课时是免费的吗？
是的 — 「字段默认值」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Zig Academy 课程的其余内容，请升级到 CoddyKit PRO。 Zig Academy 课程共包含 4 节课。
「字段默认值」这节课中我会学到什么？
无需重复代码即可初始化字段。 你通过在浏览器中直接运行的动手代码来练习 Zig Academy，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 Zig Academy 需要有经验吗？
无需任何先前经验。CoddyKit 上的 Zig Academy 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 3 节课，共 4 节。
「字段默认值」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 Zig Academy 课中编写并运行代码吗？
能。每节 Zig Academy 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。