英文:
Golang type embedding implement
问题
我有一个类型T，它嵌入了类型B，并且*B实现了接口I。*T可以赋值给类型I的变量，但对于类型T来说不行，这是否意味着(*T)的方法集包含了B的值接收器和指针接收器？
package main
import (
"fmt"
)
type I interface {
Foo()
}
type B struct {}
type T struct {
B
}
func (a *B) Foo() {
fmt.Println("Bar")
}
func main() {
t := T{B{}}
// var i I = t -> error
var i I = &t
i.Foo()
}
英文:
I have a type T which embed type B, and *B implements I. *T can be assigned to a variable of type I but not in the case of T, does this mean (*T)'s method set contains both value and pointer receiver of B?
package main
import (
"fmt"
)
type I interface {
Foo()
}
type B struct {}
type T struct {
B
}
func (a *B) Foo() {
fmt.Println("Bar")
}
func main() {
t := T{B{}}
// var i I = t -> error
var i I = &t
i.Foo()
}
答案1
得分: 8
是的，*T 的方法集中包含了接收者为 B 和 *B 的方法。
给定一个结构体类型
S和一个定义类型T，被提升的方法将按照以下规则包含在结构体的方法集中：
- 如果
S包含一个嵌入字段T，则S和*S的方法集都包含了接收者为T的被提升的方法。*S的方法集还包含了接收者为*T的被提升的方法。- 如果
S包含一个嵌入字段*T，则S和*S的方法集都包含了接收者为T或*T的被提升的方法。
英文:
Yes, method set of *T contains methods with receiver B and *B.
> Given a struct type S and a defined type T, promoted methods are included in the method set of the struct as follows:
>
> - If S contains an embedded field T, the method sets of S and *S both include promoted methods with receiver T. The method set of *S also includes promoted methods with receiver *T.
> - If S contains an embedded field *T, the method sets of S and *S both include promoted methods with receiver T or *T.
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