引发错误
发出操作出错的信号
引发错误 是 CoddyKit 上的免费 Mojo Academy 课时。 这是第 1 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 Mojo Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Mojo 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。
When Things Go Wrong
Sometimes a function hits a situation it cannot handle, like a missing file or bad input. Mojo lets you signal that with an error. ⚠️
The raise Keyword
To signal a failure, you use the raise keyword. It stops the current work and reports that something went wrong.
raise Error("something went wrong")Errors Carry a Message
When you raise, you pass a short message describing the problem. Whoever handles the error can read that text.
raise Error("file not found")Raising Inside a Function
A function can raise when its input is invalid. Here a negative amount is rejected before any further work happens.
fn withdraw(amount: Int) raises:
if amount < 0:
raise Error("amount must be positive")Raising Stops Execution
Once raise runs, the rest of the function is skipped. Control jumps out, looking for code that can deal with the error.
Why Not Just Return -1?
Returning a magic value like -1 is easy to ignore. An error cannot be silently skipped, making failures far harder to miss.
Errors Travel Up
An unhandled error keeps moving up through the callers until something catches it. This is called propagation.
Guarding Your Inputs
Raising early on bad input is a clean habit. Check the values first, then raise before the real logic ever runs.
if name == "":
raise Error("name is required")One Clear Reason
Give each raise a clear, specific message. Good wording turns a crash into a helpful clue for whoever debugs it.
Errors Are Not Crashes
A raised error is a structured signal, not a random crash. Your program can recover from it instead of just dying.
Raise When You Can't Continue
The rule of thumb: raise only when a function truly cannot finish its job correctly. Don't raise for normal outcomes.
Quick Check
Think about what the raise keyword actually does in Mojo.
Recap
You learned to signal failures with raise, attach a clear message, and let errors stop bad work instead of returning magic values. 🎯
常见问题解答
「引发错误」课时是免费的吗？
是的 — 「引发错误」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 Mojo Academy 课程的其余内容，请升级到 CoddyKit PRO。 Mojo Academy 课程共包含 4 节课。
「引发错误」这节课中我会学到什么？
发出操作出错的信号 你通过在浏览器中直接运行的动手代码来练习 Mojo 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 Mojo Academy 需要有经验吗？
无需任何先前经验。CoddyKit 上的 Mojo 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 1 节课，共 4 节。
「引发错误」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 Mojo Academy 课中编写并运行代码吗？
能。每节 Mojo 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。