go - 为父 golang 结构字段赋值

Question

有两种情况:

type A struct {
    A_FIELD  string
}
type B struct {
    A
    B_FIELD  string
}

func main() {
    b := &B{
        A_FIELD: "aaaa_field",
        B_FIELD: "bbbb_field",
    } 
}

和

type A struct {
    A_FIELD  string
}
type B struct {
    A
    B_FIELD  string
}

func main() {
    b := &B{}
    b.A_FIELD = "aaaa_field"
    b.B_FIELD = "bbbb_field"
    fmt.Printf("Good!")
}

为什么第二个可以用，而第一个不行？我收到编译时异常。我应该如何更改第一个才能工作？

Answer 1

Why the second one is working, but the first one is not?

因为

b.A_FIELD = "aaaa_field"

实际上是

b.A.A_FIELD = "aaaa_field"

伪装。

How should I change first one to work?

func main() {
    b := &B{
        A: A{
            A_FIELD: "aaaa_field",
        },
        B_FIELD: "bbbb_field",
    }
}

你应该阅读 how embedding work在 Effective Go 上。