Fixed something wrong.
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Oling Cat
272
2.5.md
272
2.5.md
@@ -6,23 +6,23 @@
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package main
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import "fmt"
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type Rectangle struct {
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width, height float64
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}
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func area(r Rectangle) float64 {
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return r.width*r.height
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}
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func main() {
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r1 := Rectangle{12, 2}
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r2 := Rectangle{9, 4}
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fmt.Println("Area of r1 is: ", area(r1))
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fmt.Println("Area of r2 is: ", area(r2))
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width, height float64
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}
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这个代码是可以计算出来长方形的面积，但是area不是作为Rectangle的一个方法(类似面向对象里面的方法)实现的, 而是Rectangle的对象(r1,r2)作为函数的一个参数传入，然后计算获取的。
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func area(r Rectangle) float64 {
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return r.width*r.height
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}
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func main() {
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r1 := Rectangle{12, 2}
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r2 := Rectangle{9, 4}
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fmt.Println("Area of r1 is: ", area(r1))
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fmt.Println("Area of r2 is: ", area(r2))
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}
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这个代码是可以计算出来长方形的面积，但是area不是作为Rectangle的一个方法（类似面向对象里面的方法）实现的，而是Rectangle的对象（r1,r2）作为函数的一个参数传入，然后计算获取的。
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这样实现有什么问题，当然没有问题咯，但是当你代码里面增加一个圆形、正方形、多边形等的时候，然后你又想计算他们的面积的时候怎么办啊？那就增加新的函数咯，但是函数名你就必须要跟着换了，你就要把函数名变成`area_rectangle, area_circle, area_triangle...`
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@@ -34,9 +34,9 @@
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>“A method is a function with an implicit first argument, called a receiver.“
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method的语法如下：
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func (ReceiverType r) func_name (parameters) (results)
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method的语法如下：
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func (ReceiverType r) funcName(parameters) (results)
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下面我们用最开始的例子用method来实现：
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@@ -45,36 +45,36 @@ method的语法如下：
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"fmt"
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"math"
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)
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type Rectangle struct {
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width, height float64
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width, height float64
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}
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type Circle struct {
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radius float64
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radius float64
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}
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func (r Rectangle) area() float64 {
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return r.width*r.height
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return r.width*r.height
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}
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func (c Circle) area() float64 {
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return c.radius * c.radius * math.Pi
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return c.radius * c.radius * math.Pi
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}
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func main() {
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r1 := Rectangle{12, 2}
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r2 := Rectangle{9, 4}
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c1 := Circle{10}
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c2 := Circle{25}
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fmt.Println("Area of r1 is: ", r1.area())
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fmt.Println("Area of r2 is: ", r2.area())
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fmt.Println("Area of c1 is: ", c1.area())
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fmt.Println("Area of c2 is: ", c2.area())
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r1 := Rectangle{12, 2}
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r2 := Rectangle{9, 4}
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c1 := Circle{10}
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c2 := Circle{25}
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fmt.Println("Area of r1 is: ", r1.area())
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fmt.Println("Area of r2 is: ", r2.area())
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fmt.Println("Area of c1 is: ", c1.area())
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fmt.Println("Area of c2 is: ", c2.area())
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}
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在使用method的时候重要注意几点
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- 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
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@@ -83,8 +83,8 @@ method的语法如下：
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那是不是method只能作用在struct上面呢？当然不是咯，他可以定义在任何你自定义的类型、内置类型、struct等各种类型上面。这里你是不是有点迷糊了，什么叫自定义类型，自定义类型不就是struct嘛，不是这样的哦，struct只是自定义类型里面一种比较特殊的类型而已，还有其他自定义类型申明，可以通过如下这样的申明来实现。
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type type_name type_literal
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type typeName typeLiteral
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请看下面这个申明自定义类型的代码
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type ages int
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@@ -94,12 +94,12 @@ method的语法如下：
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type months map[string]int
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m := months {
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"January":31,
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"February":28,
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...
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"December":31,
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}
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"January":31,
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"February":28,
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...
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"December":31,
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}
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看到了吗？简单的很吧，这样你就可以在自己的代码里面定义有意义的类型了，实际上只是一个定义了一个别名,有点类似于c中的typedef，例如上面ages替代了int
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好了，让我们回到`method`
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@@ -110,75 +110,75 @@ method的语法如下：
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import "fmt"
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const(
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WHITE = iota
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BLACK
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BLUE
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RED
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YELLOW
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WHITE = iota
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BLACK
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BLUE
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RED
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YELLOW
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)
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type Color byte
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type Box struct {
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width, height, depth float64
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color Color
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width, height, depth float64
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color Color
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}
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type BoxList []Box //a slice of boxes
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func (b Box) Volume() float64 {
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return b.width * b.height * b.depth
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return b.width * b.height * b.depth
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}
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func (b *Box) SetColor(c Color) {
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b.color = c
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b.color = c
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}
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func (bl BoxList) BiggestsColor() Color {
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v := 0.00
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k := Color(WHITE)
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for _, b := range bl {
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if b.Volume() > v {
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v = b.Volume()
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k = b.color
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}
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}
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return k
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v := 0.00
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k := Color(WHITE)
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for _, b := range bl {
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if b.Volume() > v {
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v = b.Volume()
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k = b.color
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}
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}
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return k
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}
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func (bl BoxList) PaintItBlack() {
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for i, _ := range bl {
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bl[i].SetColor(BLACK)
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}
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for i, _ := range bl {
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bl[i].SetColor(BLACK)
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}
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}
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func (c Color) String() string {
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strings := []string {"WHITE", "BLACK", "BLUE", "RED", "YELLOW"}
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return strings[c]
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strings := []string {"WHITE", "BLACK", "BLUE", "RED", "YELLOW"}
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return strings[c]
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}
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func main() {
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boxes := BoxList {
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Box{4, 4, 4, RED},
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Box{10, 10, 1, YELLOW},
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Box{1, 1, 20, BLACK},
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Box{10, 10, 1, BLUE},
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Box{10, 30, 1, WHITE},
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Box{20, 20, 20, YELLOW},
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}
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fmt.Printf("We have %d boxes in our set\n", len(boxes))
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fmt.Println("The volume of the first one is", boxes[0].Volume(), "cm³")
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fmt.Println("The color of the last one is",boxes[len(boxes)-1].color.String())
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fmt.Println("The biggest one is", boxes.BiggestsColor().String())
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fmt.Println("Let's paint them all black")
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boxes.PaintItBlack()
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fmt.Println("The color of the second one is", boxes[1].color.String())
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fmt.Println("Obviously, now, the biggest one is", boxes.BiggestsColor().String())
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boxes := BoxList {
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Box{4, 4, 4, RED},
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Box{10, 10, 1, YELLOW},
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Box{1, 1, 20, BLACK},
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Box{10, 10, 1, BLUE},
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Box{10, 30, 1, WHITE},
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Box{20, 20, 20, YELLOW},
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}
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fmt.Printf("We have %d boxes in our set\n", len(boxes))
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fmt.Println("The volume of the first one is", boxes[0].Volume(), "cm³")
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fmt.Println("The color of the last one is",boxes[len(boxes)-1].color.String())
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fmt.Println("The biggest one is", boxes.BiggestsColor().String())
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fmt.Println("Let's paint them all black")
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boxes.PaintItBlack()
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fmt.Println("The color of the second one is", boxes[1].color.String())
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fmt.Println("Obviously, now, the biggest one is", boxes.BiggestsColor().String())
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}
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上面这个例子我们通过const定义了一些常量，然后定义了一些自定义类型
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- Color作为byte的别名
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@@ -223,34 +223,34 @@ method的语法如下：
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package main
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import "fmt"
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type Human struct {
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name string
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age int
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phone string
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name string
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age int
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phone string
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}
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type Student struct {
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Human //匿名字段
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school string
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Human //匿名字段
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school string
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}
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type Employee struct {
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Human //匿名字段
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company string
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Human //匿名字段
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company string
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}
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//在human上面定义了一个method
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func (h *Human) SayHi() {
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fmt.Printf("Hi, I am %s you can call me on %s\n", h.name, h.phone)
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fmt.Printf("Hi, I am %s you can call me on %s\n", h.name, h.phone)
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}
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func main() {
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mark := Student{Human{"Mark", 25, "222-222-YYYY"}, "MIT"}
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sam := Employee{Human{"Sam", 45, "111-888-XXXX"}, "Golang Inc"}
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mark.SayHi()
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sam.SayHi()
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mark := Student{Human{"Mark", 25, "222-222-YYYY"}, "MIT"}
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sam := Employee{Human{"Sam", 45, "111-888-XXXX"}, "Golang Inc"}
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mark.SayHi()
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sam.SayHi()
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}
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###method重载
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@@ -258,49 +258,49 @@ method的语法如下：
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package main
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import "fmt"
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type Human struct {
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name string
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age int
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phone string
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name string
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age int
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phone string
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}
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type Student struct {
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Human //匿名字段
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school string
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Human //匿名字段
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school string
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}
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type Employee struct {
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Human //匿名字段
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company string
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Human //匿名字段
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company string
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}
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//Human定义method
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func (h *Human) SayHi() {
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fmt.Printf("Hi, I am %s you can call me on %s\n", h.name, h.phone)
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fmt.Printf("Hi, I am %s you can call me on %s\n", h.name, h.phone)
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}
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//Employee的method重载Human的method
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func (e *Employee) SayHi() {
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fmt.Printf("Hi, I am %s, I work at %s. Call me on %s\n", e.name,
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e.company, e.phone) //Yes you can split into 2 lines here.
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fmt.Printf("Hi, I am %s, I work at %s. Call me on %s\n", e.name,
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e.company, e.phone) //Yes you can split into 2 lines here.
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}
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func main() {
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mark := Student{Human{"Mark", 25, "222-222-YYYY"}, "MIT"}
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sam := Employee{Human{"Sam", 45, "111-888-XXXX"}, "Golang Inc"}
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mark.SayHi()
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sam.SayHi()
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mark := Student{Human{"Mark", 25, "222-222-YYYY"}, "MIT"}
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sam := Employee{Human{"Sam", 45, "111-888-XXXX"}, "Golang Inc"}
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mark.SayHi()
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sam.SayHi()
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}
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上面的代码设计的是如此的美妙，让人不自觉的为Go的设计惊叹！
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通过这些内容，我们可以设计出基本的面向对象的程序了，但是Go里面的面向对象是如此的简单，没有任何的私有、共有关键字，通过大小写来实现(大写开头的为共有，小写开头的为私有)，方法也同样适用这个原则。
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通过这些内容，我们可以设计出基本的面向对象的程序了，但是Go里面的面向对象是如此的简单，没有任何的私有、共有关键字，通过大小写来实现(大写开头的为共有，小写开头的为私有)，方法也同样适用这个原则。
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## links
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* [目录](<preface.md>)
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* 上一章: [struct类型](<2.4.md>)
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* 下一节: [interface](<2.6.md>)
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## LastModified
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## LastModified
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* $Id$
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