Struct

Basic

• 機制是 copy struct
• pointer receiver: 兩個 memory address 是一樣的

package main

import (
    "fmt"
)

func main() {
    student := Student{Age: 18}
    fmt.Printf("memory address: %p\n", &student)

    student.change()
    fmt.Println(student.Age)
}

type Student struct {
    Age int
}

func (student *Student) change() {
    student.Age = 25
    fmt.Printf("memory address: %p\n", student) // %p -> pointer
}

Anonymous

package main

import (
    "fmt"
)

func main() {
    // 1.
    var test1 struct {
        name string
        age  int
    }
    test1.age = 15
    test1.name = "test"
    fmt.Println(test1)

    // 2.
    test2 := struct {
        name string
        age  int
    }{
        name: "test",
        age:  15,
    }
    fmt.Println(test2)
}

Embedded

把一個 struct 寫在另一個 struct 裡面，稱作 embedded (嵌入)

• promoted 被提升 → 外部 struct 可以直接用內部 struct 的 fields

package main

import (
    "fmt"
)

func main() {
    s := Student{}
    s.Age = 27
    s.Name.FirstName = "Nano"
    s.LastName = "Wang" // 可以直接用 -> promoted

    fmt.Println(s)
}

type Student struct {
    Name // anonymous field -> embedded
    Age  int
}

type Name struct {
    FirstName string
    LastName  string
}

Struct Tag

How To Use Struct Tags in Go | DigitalOcean