Golang anonymous struct field example .

Anonymous struct field and method and interface

What is anonymous field

First we can see an example:

package main

import "fmt"

type Animal struct {
    Name string
    Sex  string //male or female
}

type Dog struct {
    Animal
    Kind string
}

type Husky struct {
    Dog
    Cute bool
}

func (d Dog) Greet() {
    fmt.Printf("Hello, I'm a %s\n", d.Kind)
}

type Pet interface {
    Greet()
}

func petGreet(p Pet) {
    p.Greet()
}

func main() {
    d := Dog{Animal: Animal{Name: "旺财", Sex: "male"}, Kind: "Husky"}
    h := &Husky{Dog: d, Cute: true}
    fmt.Println(h.Name)
    fmt.Println(h.Dog.Name)
    fmt.Println(h.Animal.Name)
    fmt.Println(h.Dog.Animal.Name)
    d.Greet()
    h.Greet()
    h.Dog.Greet()

    petGreet(d)
    petGreet(h)
}

Output would be:

旺财
旺财
旺财
旺财
Hello, I'm a Husky
Hello, I'm a Husky
Hello, I'm a Husky
Hello, I'm a Husky
Hello, I'm a Husky

We can conclude the features of anonymous filed, these should be the motivation or benefits for it.

1. anonymous field is a struct field without specifing the field name.
2. An anonymous field has an implicit name of the field type.
3. We can access field and methods of Anonymous fileds using shortcut notation without the implicit filed name. Just like h.Greet() is equvalent to h.Dog.Greet()
4. if the anonymous field implements or satisfys some interface, so does the whole struct