golang中值类型的嵌入式字段和指针类型的嵌入式字段

总结：

　　1. 值类型的嵌入式字段，该类型拥有值类型的方法集，没有值指针类型的方法集

　　2. 指针类型的嵌入式字段，该类型拥有值指针类型的方法集，没有值类型的方法集，并且，该类型的指针类型也有值指针类型的方法集

有点绕，见案例：

package main
 
import "fmt"
 
type Boss struct{}
func (b *Boss) AssignWork() {
    fmt.Println("Boss assigned work")
}
 
type Manager struct{}
func (m *Manager) PreparePowerPoint() {
    fmt.Println("PowerPoint prepared")
}
 
type BossManager struct {
    Boss  // 嵌入式字段
    Manager  // 嵌入式字段
}
type BossManagerUsingPointers struct {
    *Boss  // 指针类型的嵌入式字段
    *Manager  // 指针类型的嵌入式字段
}
/*
BossManager和BossManagerUsingPointers的区别？
BossManage类型没有实现这个PromotionMaterial接口，BossManage的指针类型实现了这个接口
BossManagerUsingPointers类型实现了PromotionMaterial这个接口
BossManagerUsingPointers的指针类型也是PromotionMaterial这个接口类型
*/
 
// Define an interface that requires both methods.
type PromotionMaterial interface {
    AssignWork()
    PreparePowerPoint()
}
 
func promote(pm PromotionMaterial) {
    fmt.Println("Promoted a person with promise.")
}
 
func main() {
    bm := BossManager{}
 
    // Both methods (which use pointer receivers) have been promoted to BossManager.
    bm.AssignWork()        // "Boss assigned work"
    bm.PreparePowerPoint() // "PowerPoint prepared"
 
    // However, the method set of BossManager does not include either method because:
    // 1) {Boss, Manager} are embedded as value types, not pointer types.
    // 2) This makes it so that only the pointer type *BossManager includes both methods
    // in its method set, thus making it implement interface PromotionMaterial.
 
    // promote(bm)  // Would fail with: cannot use bm (type BossManager) as type PromotionMaterial in argument to promote:
    // BossManager does not implement PromotionMaterial (AssignWork method has pointer receiver)
    // This would work if {Boss, Manager} were embedded as pointer types.
 
    promote(&bm) // Works
 
    // Lets use the struct with the embedded pointer types:
    bm2 := BossManagerUsingPointers{}
    bm2.AssignWork()        // "Boss assigned work"
    bm2.PreparePowerPoint() // "PowerPoint prepared"
    promote(bm2)            // Works
    promote(&bm2)           // Also works, since both BossManagerUsingPointers (value type) and *BossManagerUsingPointers (pointer type)
    // method sets include both methods.
}