package main
import (
"fmt" "math"
)
type Rectangle struct {
width, height float64
}
type Circle struct {
radius float64
}
func (r Rectangle) area() float64 {
return r.width * r.height
}
func (c Circle) area() float64 {
return c.radius * c.radius * math.Pi
}
func main() {
r1 := Rectangle{12, 2}
r2 := Rectangle{9, 4}
c1 := Circle{10}
c2 := Circle{25}
fmt.Println("Area of r1 is: ", r1.area())
fmt.Println("Area of r2 is: ", r2.area())
fmt.Println("Area of c1 is: ", c1.area())
fmt.Println("Area of c2 is: ", c2.area())
}
输出结果为：
Area of r1 is: 24
Area of r2 is: 36
Area of c1 is: 314.1592653589793
Area of c2 is: 1963.4954084936207
使用method的时候重要注意以下几点。
● 虽然method的名字一模一样，但是如果接收者不一样，那么method就不一样。
● method里面可以访问接收者的字段。
● 调用method通过访问，就像struct里面访问字段一样。
package main
import "fmt"
const (
WHITE = iota
BLACK
BLUE
RED
YELLOW
)
type Color byte type Box struct {
width, height, depth float64
color Color
}
type BoxList []Box // a slice of boxes
/* Box Volume() SetColor(c Color) */
func (b Box) Volume() float64 {
return b.width * b.height * b.depth
}
func (b *Box) SetColor(c Color) {
b.color = c
}
/* BoxList BiggestsColor() PaintItBlack() */
func (bl BoxList) BiggestsColor() Color {
v := 0.00
k := Color(WHITE) // k := byte(WHITE)
for _, b := range bl {
if b.Volume() > v {
v = b.Volume() k = b.color
}
}
return k
}
func (bl BoxList) PaintItBlack() {
for i, _ := range bl {
bl[i].SetColor(BLACK)
}
}
/* Color String() */
func (c Color) String() string {
strings := []string{"WHITE", "BLACK", "BLUE", "RED", "YELLOW"} return strings[c]
}
func main() {
boxes := BoxList{ Box{4, 4, 4, RED},
Box{10, 10, 1, YELLOW},
Box{1, 1, 20, BLACK},
Box{10, 10, 1, BLUE},
Box{10, 30, 1, WHITE},
Box{20, 20, 20, YELLOW},
}
fmt.Printf("We have %d boxes in our set\n", len(boxes)) fmt.Println("The volume of the first one is", boxes[0].Volume(), "cm3")
fmt.Println("The color of the last one is", boxes[len(boxes)-1].color.String()) fmt.Println("The biggest one is", boxes.BiggestsColor().String())
fmt.Println("Let`s paint them all black") boxes.PaintItBlack()
fmt.Println("The color of the second one is", boxes[1].color.String()) fmt.Println("Obviously, now, the biggest one is",
boxes.BiggestsColor().String())
}
输出结果为：
We have 6 boxes in our set
The volume of the first one is 64 cm3
The color of the last one is YELLOW
The biggest one is YELLOW
Let`s paint them all black
The color of the second one is BLACK
Obviously, now, the biggest one is BLACK
上面的代码通过const定义了一些常量，然后定义了一些自定义类型。
● Color作为byte的别名。
● 定义了一个struct:Box，含有三个长宽高字段和一个颜色属性。
● 定义了一个slice:BoxList，含有Box。然后以上面的自定义类型为接收者定义了一些method。
● Volume()定义了接收者为Box，返回Box的容量。
● SetColor(cColor)，把Box的颜色改为c。
● BiggestsColor()定在在BoxList上面，返回list里面容量最大的颜色。
● PaintItBlack()把BoxList里面所有Box的颜色全部变成黑色。
● String()定义在Color上面，返回Color的具体颜色（字符串格式）。
