go - 嵌入式结构还是嵌套结构？

Question

下面的代码是 Embedded Struct 或 Nested Struct 还是其他的例子？并且我们是否在另一种类型结构 (secretAgent) 中使用一种结构类型(人)？

package main

import "fmt"

type person struct {
    first string
    last  string
    age   int
}

type secretAgent struct {
    person
    ltk bool
}

func main() {

    sa1 := secretAgent{
        person: person{
            first: "James",
            last:  "Bond",
            age:   32,
        },
        ltk: true,
    }

    fmt.Println(sa1.first, sa1.last, sa1.age, sa1.ltk)
}

Answer 1

spec将其称为嵌入字段:

A field declared with a type but no explicit field name is called an embedded field. [...]

struct {
    T1        // field name is T1
    ...
}

我不确定您所说的“在另一种结构类型中使用一种结构类型”是什么意思，但是您通过将一种结构类型嵌入另一种结构类型来在 secretAgent 中使用 person .在大多数情况下，person 字段也被提升为表现得像 secretAgent 的成员:

Promoted fields act like ordinary fields of a struct except that they cannot be used as field names in composite literals of the struct.

所以你可以说:

sa1 := secretAgent{
    person: person{
        first: "James",
        last:  "Bond",
        age:   32,
    },
    ltk: true,
}

和

sa1.first

但不是:

sa1 := secretAgent{
    first: "James",
    last:  "Bond",
    age:   32,
    ltk: true,
}

您还可以通过 person 显式引用嵌入的 person 字段:

// As a promoted field...
sa1.first
// More explicitly...
sa1.person.first