Golang创建构造函数的方法超详细讲解

type Book struct {
  title string
  pages int
}
// creating a new struct instance
b := Book{}
// creating a pointer to a struct instance
bp := &Book{}
// creating an empty value
nothing := struct{}{}

b := Book{
  title: "Julius Caesar",
  pages: 322,
}

type Pizza struct {
  slices int
  toppings []string
}
somePizza := Pizza{
  slices: 6,
  toppings: []string{"pepperoni"},
}
otherPizza := Pizza{
  slices: 6,
  toppings: []string{"onion", "pineapple"},
}

func NewPizza(toppings []string) () {
  if toppings == nil {
    toppings = []string{}
  }
  return Pizza{
    slices: 6,
    toppings: toppings,
  }
}

func NewRemotePizza(url string) (Pizza, error) {
  // toppings are received from a remote URL, which may fail
  toppings, err := getToppings(url)
  if err != nil {
    // if an error occurs, return the wrapped error along with an empty
    // Pizza instance
    return Pizza{}, fmt.Errorf("could not construct new Pizza: %v", err)
  }
  return Pizza{
    slices:   6,
    toppings: toppings,
  }, nil
}

// Pizza implements Bakeable
type Bakeable interface {
	Bake()
}
type Pizza struct {
	slices   int
	toppings []string
	isBaked  bool
}
func (p Pizza) Bake() {
	p.isBaked = true
}
// this constructor will return a `Bakeable`
// and not a `Pizza`
func NewUnbakedPizza(toppings []string) Bakeable {
	return Pizza{
		slices:   6,
		toppings: toppings,
	}
}

package pizza
type Pizza struct {
  // ...
}
func New(toppings []string) Pizza {
  // ...
}