Go 語言中接口和多態(tài)的核心是通過隱式接口實(shí)現(xiàn)和方法集合達(dá)成靈活多態(tài)行為。1. 接口定義行為，任何類型只要實(shí)現(xiàn)其方法即自動滿足接口，無需顯式聲明；2. 多態(tài)體現(xiàn)為同一接口方法在不同類型上有不同實(shí)現(xiàn)，通過接口統(tǒng)一調(diào)用；3. 空接口 interface{} 或 any 可接收任意類型，配合類型斷言或類型 switch 還原具體類型；4. 推薦使用小而專注的接口，如 io.Reader 和 io.Writer，提升組合性和復(fù)用性。這些機(jī)制使 Go 在不依賴?yán)^承的情況下實(shí)現(xiàn)高效、解耦的多態(tài)設(shè)計。
Go 語言中的接口（Interfaces）和多態(tài)（Polymorphism）是構(gòu)建靈活、可擴(kuò)展程序的核心機(jī)制。雖然 Go 不是傳統(tǒng)意義上的面向?qū)ο笳Z言，但它通過接口和組合的方式，實(shí)現(xiàn)了類似多態(tài)的行為，且更加簡潔和實(shí)用。
接口：定義行為，而非結(jié)構(gòu)
在 Go 中，接口是一種類型，它定義了一組方法簽名。任何類型只要實(shí)現(xiàn)了這些方法，就自動“滿足”該接口，無需顯式聲明。這種“隱式實(shí)現(xiàn)”是 Go 接口設(shè)計的一大特色。
type Speaker interface {
Speak() string
}
type Dog struct{}
type Cat struct{}
func (d Dog) Speak() string {
return "Woof!"
}
func (c Cat) Speak) string {
return "Meow!"
}這里，Dog 和 Cat 都沒有說“我實(shí)現(xiàn)了 Speaker”，但因?yàn)樗鼈兌加?Speak() 方法，返回值匹配，所以它們自動成為 Speaker 的實(shí)現(xiàn)類型。
你可以這樣使用：
func MakeSound(s Speaker) {
fmt.Println(s.Speak())
}
MakeSound(Dog{}) // Woof!
MakeSound(Cat{}) // Meow!這就是多態(tài)的體現(xiàn)：同一個函數(shù) MakeSound 可以處理不同類型的對象，只要它們滿足接口。
多態(tài)：同一接口，多種實(shí)現(xiàn)
多態(tài)在 Go 中不是通過繼承，而是通過接口和方法實(shí)現(xiàn)來達(dá)成的。你不需要知道具體類型，只需要它能“做某事”（即實(shí)現(xiàn)接口方法）。
比如，處理一組不同的動物：
animals := []Speaker{Dog{}, Cat{}, Dog{}}
for _, a := range animals {
fmt.Println(a.Speak())
}輸出：
Woof! Meow! Woof!
盡管 animals 切片中包含不同具體類型，但由于它們都實(shí)現(xiàn)了 Speaker，所以可以統(tǒng)一處理。這就是多態(tài)的力量——調(diào)用相同的方法，產(chǎn)生不同的行為。
空接口與類型斷言
Go 中的 interface{}（或在 Go 1.18+ 中的 any）是“萬能接口”，所有類型都滿足它。這在需要處理任意類型時很有用，比如函數(shù)參數(shù)或容器。
func PrintAnything(v interface{}) {
fmt.Println(v)
}但使用空接口時，你可能會需要還原具體類型，這時就要用類型斷言：
if s, ok := v.(Speaker); ok {
fmt.Println("It can speak:", s.Speak())
} else {
fmt.Println("Not a speaker")
}或者用類型 switch：
switch x := v.(type) {
case Dog:
fmt.Println("It's a dog:", x.Speak())
case Cat:
fmt.Println("It's a cat:", x.Speak())
default:
fmt.Println("Unknown type")
}小而專注的接口
Go 倡導(dǎo)使用小接口。最經(jīng)典的例子是 io.Reader 和 io.Writer：
type Reader interface {
Read(p []byte) (n int, err error)
}只要一個類型能讀數(shù)據(jù)到字節(jié)切片，它就是 Reader。文件、網(wǎng)絡(luò)連接、字符串緩沖區(qū)都可以實(shí)現(xiàn)它。這種設(shè)計讓組合變得非常自然。
比如，你可以寫一個函數(shù)處理任何 Reader：
func ReadAndPrint(r io.Reader) {
data := make([]byte, 100)
n, _ := r.Read(data)
fmt.Println(string(data[:n]))
}這個函數(shù)可以傳 *os.File、*bytes.Buffer、net.Conn 等任何實(shí)現(xiàn)了 Read 的類型。
總結(jié)
- 接口是方法的集合，隱式實(shí)現(xiàn)。
- 多態(tài)通過接口實(shí)現(xiàn)：不同類型對同一方法調(diào)用表現(xiàn)出不同行為。
- 不依賴?yán)^承，而是依賴組合和接口滿足。
- 小接口更容易復(fù)用，更符合 Go 的哲學(xué)。
基本上就這些。Go 的接口和多態(tài)不復(fù)雜，但用好了能讓代碼更清晰、更解耦。
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