Mojo Academy · 课时

读取函数签名

通过声明理解函数

读取函数签名 是 CoddyKit 上的免费 Mojo Academy 课时。这是第 4 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。

The Signature Is the Contract

A function's signature is its first line: the name, the parameters, and the return type. Read it well and you know how to call the function.

fn area(width: Int, height: Int) -> Int:

Spotting the Name

Right after fn or def comes the name. It should hint at what the function does, like area, parse, or connect.

fn parse(text: String) -> Int:

Reading the Parameters

Inside the parentheses are the parameters the function expects. Each pairs a name with a type, telling you what to pass in.

fn area(width: Int, height: Int) -> Int:

Parameter Types Guide You

The type after each colon tells you the kind of value to send. width: Int means area expects a whole number, not text.

fn greet(name: String, times: Int): ...

The Return Type Arrow

The arrow points to what the function gives back. Here -> Int promises an integer result you can store or print.

fn area(width: Int, height: Int) -> Int:

No Arrow Means No Value

When there is no arrow, the function returns None. It does its work for the side effect, like printing, not for a result.

fn log(msg: String):
    print(msg)

Defaults in the Signature

An equals sign in a parameter marks a default. It signals the value is optional and shows the fallback Mojo will use.

fn open(path: String, mode: String = "r"): ...

raises Warns of Failure

A raises keyword on the signature means the function can fail. That tells you to wrap your call in error handling.

fn read(path: String) raises -> String:

fn vs def at a Glance

The opening word matters. fn means strict and typed; def means flexible and Python-like. The signature tells you which contract you are under.

def loose(x): ...
fn strict(x: Int) -> Int: ...

A Signature as Mini-Docs

Before reading any body, the signature already answers what goes in and what comes out. Treat it as the function's summary.

Putting It All Together

Name, parameters, defaults, return type, and raises: each part of the signature is a clue. Together they tell you exactly how to use the function.

fn fetch(url: String, retries: Int = 3) raises -> String:

Quick Check

In a Mojo signature, what does the part after the arrow tell you?

Recap: Read Before You Call

A signature shows the name, parameters with types, any defaults, the return type, and raises. Read it first and calling correctly becomes easy.

常见问题解答

「读取函数签名」课时是免费的吗？

是的 — 「读取函数签名」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。

「读取函数签名」这节课中我会学到什么？

通过声明理解函数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 4 节课，共 4 节。

「读取函数签名」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。

此课程中的所有课时

← 返回 Mojo Academy