在Go語言中，接口是一種定義行為而不指定實現方式的類型。接口由方法簽名組成，任何實現這些方法的類型都自動滿足該接口。例如，定義一個Speaker接口包含Speak()方法，則所有實現該方法的類型均可視為Speaker。接口適用於編寫通用函數、抽象實現細節(jié)和測試中使用mock對象。定義接口使用interface關鍵字並列出方法簽名，無需顯式聲明類型實現了接口。常見用例包括日誌、格式化、不同數據庫或服務的抽象，以及通知系統(tǒng)等。例如，Dog和Robot類型均可實現Speak方法，並傳遞給同一個Announce函數處理。

Interfaces in Go are a way to define behavior without specifying how that behavior is implemented. They let different types implement the same set of methods, allowing you to write more flexible and reusable code.

What Exactly Is an Interface?

An interface in Go is a collection of method signatures. Any type that implements all the methods in the interface automatically satisfies that interface — no need for explicit declaration.

For example, if you have an interface like this:

 type Speaker interface {
    Speak() string
}

Then any type that has a Speak() method returning a string can be treated as a Speaker .

This makes interfaces powerful for writing generic functions that can work with many types, as long as those types follow the expected behavior.

How Do You Define an Interface?

Defining an interface is straightforward. You use the interface keyword and list out the method signatures it should include.

Here's a basic structure:

 type [InterfaceName] interface {
    [MethodName]([InputTypes]) [ReturnTypes]
    // more methods...
}

A few things to keep in mind:

• Method names must be unique within the interface.
• Input and return types must be specified clearly.
• Interfaces can be empty (like interface{} ), which means they accept any type.

You don't tell a type that it "implements" the interface. It just does — automatically — when it has the right methods.

When Should You Use Interfaces?

Interfaces are useful when you want to group types based on their behavior rather than their data structure.

Common use cases include:

• Writing generic functions that handle multiple types (eg, logging, formatting).
• Abstracting away implementation details (like working with different kinds of databases or services).
• Enabling mocking in tests by replacing real implementations with fake ones.

For instance, if you're building a notification system, you might define a Notifier interface with a Send(message string) method. Then you can have different notifiers — email, SMS, Slack — each implementing that same method in their own way.

A Quick Example

Let's say you have two types: Dog and Robot .

 type Dog struct{}

func (d Dog) Speak() string {
    return "Woof!"
}

type Robot struct{}

func (r Robot) Speak() string {
    return "Beep boop."
}

Both have a Speak() method. So you can write a function like this:

 func Announce(s Speaker) {
    fmt.Println(s.Speak())
}

Now, both Dog{} and Robot{} can be passed into Announce . That's the flexibility interfaces give you.

It's not magic — it's just about matching method signatures.

That's basically how interfaces work in Go. They're simple in concept but incredibly powerful when used well.

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