Method belog to struct
package mainimport ( "fmt" "math")type Rectangle struct{ width, height float64}type Circle struct { radius float64}func (r Rectangle) area(){ return r.width*r.height}func (c Circle) area(){ return c.radius * c.radius * math.Pi}func main(){ r1 := Rectangle{12,2} c1 := Circle{10} fmt.Println("Area of r1 is: ",r1.area())}
Noted:
the name of methods can be the same, but if the struct receivers are different, then the methods are different
calling method by
., just likestructcalling its elements.
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Not only struct, all other build-in types, self-defined types could be the object to apply methods.
Here are some examples of self-defined types:
type ages int //aliastype money float32type months map[string]int
Here is another comprehensive example:
package mainimport "fmt"const( white = iota black blue red yellow)type Color byte //uint8type Box struct{ width,height, depth float64 color Color}type BoxList []Box //a slice whose elements are boxesfunc (b Box) Volume() float64{ return b.width * b.height * b.depth}func (b *Box) SetColor(c color){ b.color = c}func (bl BoxList) BiggestColor() Color{ v := 0.00 k := Color(white) for _,b := range bl{ //_,b corresponding to index and value, b is the strcuts if bv := b.Volume();bv>v{ v = bv k = b.color } } return k}func (bl BoxList) PaintItBlack(){ for i := range bl{ //here i is index, we skip the value, we can also write like this: //fot _,b := range bl bl[i].SetColor(black) //b.SeetColor(black) }}func (c Color) String() string{ strings := []string {"white","black","blue","red","yellow"} return string[c]}
Use pointers as receiver
func (b *Box) SetColor(c color){ b.color = c}
Here we may use *b.color instead, cause the input is a pointer(the address), however golang knows what we want to do, so we do not need to take too much time specifying those troublesome issues.
Likely, we may also use &bl[i] since the receiver of SetColor is a pointer(address), but similarily, do not focus on those details.
func (bl BoxList) PaintItBlack(){ for i := range bl{ //here i is index, we skip the value, we can also write like this: //fot _,b := range bl bl[i].SetColor(black) //b.SeetColor(black) }}
Inherit
If the embeded segment realize some methods, then the struct who includes it can inherit those methods, too.
package mainimport "fmt"type Human struct{ name string age int phone string}type Student struct{ Human school string}func (h *Human) Sayhi(){ fmt.Println("Hi, I am", h.name, "you can call me on ",h.phone)}func main(){ make := Student{Human{"Mark",25,"222-222"},"MIT"} make.SayHi()}
Overwrite
package mainimport "fmt"type Human struct{ name string age int phone string}type Student struct{ Human school string}func (h *Human) Sayhi(){ fmt.Println("Hi, I am", h.name, "you can call me on ",h.phone)}func (s *Student) Sayhi(){ fmt.Println("Hi, I am a student")}func main(){ make := Student{Human{"Mark",25,"222-222"},"MIT"} make.SayHi()}
