如何为导入的嵌入结构体字面量赋值？报错求助

先看单个文件中可正常运行的代码：

package main

import "fmt"

type foo struct {
    field1 string
    field2 string
}

type bar struct {
    foo
    field3 string
    field4 string
}

func main() {
    fooBar := bar{
        foo{
            "apples",
            "banana",
        },
        "spam",
        "eggs",
    }
    fmt.Printf("%#v\n", fooBar)
}

但拆分为跨包项目结构后：

rootproject
├── magazine
│   ├── address.go
│   └── employee.go
└── main.go

magazine/address.go代码：

package magazine

type Address struct {
    Street     string
    City       string
    State      string
    PostalCode string
}

magazine/employee.go代码：

package magazine

type Employee struct {
    Name   string
    Salary float64
    Address
}

main.go代码：

package main

import (
    "fmt"
    "magazine"
)

func main() {
    employee := magazine.Employee{
        Name:   "pogi",
        Salary: 69420,
        magazine.Address{
            Street:     "23 pukinginamo st.",
            City:       "bactol city",
            State:      "betlog",
            PostalCode: "23432",
        },
    }

    fmt.Printf("%#v\n", employee)
}

运行时会触发报错：mixture of field:value and value elements in struct literal

原因解析 #

同一个包内，嵌入结构体的类型名就是它的隐式字段名，直接用foo{...}这种值初始化是合法的——Go会自动识别这是给嵌入的foo字段赋值。

但跨包场景下，嵌入的结构体类型定义写的是Address（而非magazine.Address），所以它对应的隐式字段名是不带包名的Address。此时你写magazine.Address{...}，Go会把它当成一个未指定字段名的值初始化项，但前面已经用了Name:、Salary:这种键值对形式，混合两种初始化方式就会触发报错。

解决方法 #

方法1：指定隐式字段名（推荐）

给嵌入的结构体指定不带包名的隐式字段名Address，用键值对方式赋值：

package main

import (
    "fmt"
    "magazine"
)

func main() {
    employee := magazine.Employee{
        Name:   "pogi",
        Salary: 69420,
        Address: magazine.Address{
            Street:     "23 pukinginamo st.",
            City:       "bactol city",
            State:      "betlog",
            PostalCode: "23432",
        },
    }

    fmt.Printf("%#v\n", employee)
}

方法2：全值初始化（不推荐）

如果不想写字段名，需严格按照结构体字段的定义顺序来初始化，不能混合键值对：

employee := magazine.Employee{
    "pogi",
    69420,
    magazine.Address{
        "23 pukinginamo st.",
        "bactol city",
        "betlog",
        "23432",
    },
}

内容的提问来源于stack exchange，提问作者greg pinakapoging nilalang sa