可以扩展go struct构造函数吗？

问题描述：

given

type Rectangle struct {
    h, w int
}

func (rec *Rectangle) area() int {
    return rec.w * rec.h
}

Can you define a Square struct using Rectangle, so I can make use of area method? It is absolutely fine if it is not possible. I won't judge the language or cry or get upset. I am just learning the golang.

给出 p>

  type矩形结构{
h，w int  
} 
 
func（rec * Rectangle）area（）int {
返回rec.w * rec.h 
} 
  code>  pre> 
 
  使用Rectangle的 Square  code>结构，因此我可以使用area方法吗？ 如果不可能的话，那绝对好。 我不会评判语言，哭泣或生气。 我只是在学习golang。 p> 
  div>

答

Go isn't classically object-oriented, so it doesn't have inheritence. It also doesn't have constructors. What it does have is embedding. Thus this is possible:

type Rectangle struct {
    h, w int
}

func (rec *Rectangle) area() int {
    return rec.w * rec.h
}

type Square struct {
    Rectangle
}

The main limitation here is that there's no way for the area() method to access fields that only exist in Square.

答

I came to know that the expected way to achieve this behaviour is to write ordinary functions. see MakeSquare

type Rectangle struct {
    h, w int
}

func (rec *Rectangle) area() int {
    return rec.w * rec.h
}

type Square struct {
    Rectangle
}

func MakeSquare(x int) (sq Square) {
    sq.h = x
    sq.w = x
    return
}

func Test_square(t *testing.T) {
    sq := MakeSquare(3)
    assert.Equal(t, 9, sq.area())
}

可以扩展go struct构造函数吗？

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