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多个 defer 的执行顺序

理解延迟代码为何会逆序运行。

多个 defer 的执行顺序 是 CoddyKit 上的免费 Zig Academy 课时。这是第 2 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。

More Than One defer

A single scope can hold several defer statements. When the scope ends, Zig has to decide what order to run them in.

They Run in Reverse

Multiple defers fire in reverse order: the last one you wrote runs first, and the first one you wrote runs last.

defer one();
defer two();

Last In, First Out

This is classic LIFO behavior, just like a stack. Each defer is pushed on, and unwinding pops them off in reverse.

A Tiny Example

Here two defers run after work. The output is two then one, because the later defer unwinds before the earlier one.

defer print("one");
defer print("two");
work();

Why Reverse Makes Sense

Resources usually depend on earlier ones. Reverse order means you release the newest first, so nothing is freed while still in use.

Mirroring Acquisition

Open A, then open B. Reverse defers close B, then A, perfectly mirroring how you set them up.

a.open(); defer a.close();
b.open(); defer b.close();

Captured at Schedule Time

Each defer remembers its code in order, even though execution waits. The order is fixed the moment each defer is reached.

Skipped if Never Reached

If the scope exits before a defer line is reached, that defer was never scheduled, so it does not run at all.

if (early) return;
defer late();

Per-Scope Stacks

Each scope keeps its own defer stack. Inner scopes unwind their defers before the outer scope unwinds its own.

Predictable Teardown

Knowing the reverse rule lets you reason about cleanup precisely, so your teardown sequence is never a surprise.

A Handy Mental Model

Picture stacking plates: you add them top down, but you must remove from the top, taking the last one off first.

Quick Check

Two defers, one then two. What is the run order?

Recap

Multiple defers unwind in reverse order, like a stack, so the newest resource is released first and cleanup mirrors setup. 🔁

常见问题解答

「多个 defer 的执行顺序」课时是免费的吗？

是的 — 「多个 defer 的执行顺序」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。

「多个 defer 的执行顺序」这节课中我会学到什么？

理解延迟代码为何会逆序运行。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 2 节课，共 4 节。

「多个 defer 的执行顺序」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。

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