diff --git a/zh/02.6.md b/zh/02.6.md index 883d0f9a..5685cc91 100644 --- a/zh/02.6.md +++ b/zh/02.6.md @@ -16,73 +16,73 @@ Go语言里面设计最精妙的应该算interface,它让面向对象,内容 interface类型定义了一组方法,如果某个对象实现了某个接口的所有方法,则此对象就实现了此接口。详细的语法参考下面这个例子 ```Go - type Human struct { - name string - age int - phone string - } +type Human struct { + name string + age int + phone string +} - type Student struct { - Human //匿名字段Human - school string - loan float32 - } +type Student struct { + Human //匿名字段Human + school string + loan float32 +} - type Employee struct { - Human //匿名字段Human - company string - money float32 - } +type Employee struct { + Human //匿名字段Human + company string + money float32 +} - //Human对象实现Sayhi方法 - func (h *Human) SayHi() { - fmt.Printf("Hi, I am %s you can call me on %s\n", h.name, h.phone) - } +//Human对象实现Sayhi方法 +func (h *Human) SayHi() { + fmt.Printf("Hi, I am %s you can call me on %s\n", h.name, h.phone) +} - // Human对象实现Sing方法 - func (h *Human) Sing(lyrics string) { - fmt.Println("La la, la la la, la la la la la...", lyrics) - } +// Human对象实现Sing方法 +func (h *Human) Sing(lyrics string) { + fmt.Println("La la, la la la, la la la la la...", lyrics) +} - //Human对象实现Guzzle方法 - func (h *Human) Guzzle(beerStein string) { - fmt.Println("Guzzle Guzzle Guzzle...", beerStein) - } +//Human对象实现Guzzle方法 +func (h *Human) Guzzle(beerStein string) { + fmt.Println("Guzzle Guzzle Guzzle...", beerStein) +} - // Employee重载Human的Sayhi方法 - func (e *Employee) SayHi() { - fmt.Printf("Hi, I am %s, I work at %s. Call me on %s\n", e.name, - e.company, e.phone) //此句可以分成多行 - } +// Employee重载Human的Sayhi方法 +func (e *Employee) SayHi() { + fmt.Printf("Hi, I am %s, I work at %s. Call me on %s\n", e.name, + e.company, e.phone) //此句可以分成多行 +} - //Student实现BorrowMoney方法 - func (s *Student) BorrowMoney(amount float32) { - s.loan += amount // (again and again and...) - } +//Student实现BorrowMoney方法 +func (s *Student) BorrowMoney(amount float32) { + s.loan += amount // (again and again and...) +} - //Employee实现SpendSalary方法 - func (e *Employee) SpendSalary(amount float32) { - e.money -= amount // More vodka please!!! Get me through the day! - } +//Employee实现SpendSalary方法 +func (e *Employee) SpendSalary(amount float32) { + e.money -= amount // More vodka please!!! Get me through the day! +} - // 定义interface - type Men interface { - SayHi() - Sing(lyrics string) - Guzzle(beerStein string) - } +// 定义interface +type Men interface { + SayHi() + Sing(lyrics string) + Guzzle(beerStein string) +} - type YoungChap interface { - SayHi() - Sing(song string) - BorrowMoney(amount float32) - } +type YoungChap interface { + SayHi() + Sing(song string) + BorrowMoney(amount float32) +} - type ElderlyGent interface { - SayHi() - Sing(song string) - SpendSalary(amount float32) - } +type ElderlyGent interface { + SayHi() + Sing(song string) + SpendSalary(amount float32) +} ``` 通过上面的代码我们可以知道,interface可以被任意的对象实现。我们看到上面的Men interface被Human、Student和Employee实现。同理,一个对象可以实现任意多个interface,例如上面的Student实现了Men和YoungChap两个interface。 @@ -96,82 +96,82 @@ interface类型定义了一组方法,如果某个对象实现了某个接口 让我们来看一下下面这个例子: ```Go - package main - - import "fmt" +package main - type Human struct { - name string - age int - phone string +import "fmt" + +type Human struct { + name string + age int + phone string +} + +type Student struct { + Human //匿名字段 + school string + loan float32 +} + +type Employee struct { + Human //匿名字段 + company string + money float32 +} + +//Human实现SayHi方法 +func (h Human) SayHi() { + fmt.Printf("Hi, I am %s you can call me on %s\n", h.name, h.phone) +} + +//Human实现Sing方法 +func (h Human) Sing(lyrics string) { + fmt.Println("La la la la...", lyrics) +} + +//Employee重载Human的SayHi方法 +func (e Employee) SayHi() { + fmt.Printf("Hi, I am %s, I work at %s. Call me on %s\n", e.name, + e.company, e.phone) } - type Student struct { - Human //匿名字段 - school string - loan float32 - } - - type Employee struct { - Human //匿名字段 - company string - money float32 - } - - //Human实现SayHi方法 - func (h Human) SayHi() { - fmt.Printf("Hi, I am %s you can call me on %s\n", h.name, h.phone) - } - - //Human实现Sing方法 - func (h Human) Sing(lyrics string) { - fmt.Println("La la la la...", lyrics) - } - - //Employee重载Human的SayHi方法 - func (e Employee) SayHi() { - fmt.Printf("Hi, I am %s, I work at %s. Call me on %s\n", e.name, - e.company, e.phone) - } - - // Interface Men被Human,Student和Employee实现 - // 因为这三个类型都实现了这两个方法 - type Men interface { - SayHi() - Sing(lyrics string) - } - - func main() { - mike := Student{Human{"Mike", 25, "222-222-XXX"}, "MIT", 0.00} - paul := Student{Human{"Paul", 26, "111-222-XXX"}, "Harvard", 100} - sam := Employee{Human{"Sam", 36, "444-222-XXX"}, "Golang Inc.", 1000} - tom := Employee{Human{"Tom", 37, "222-444-XXX"}, "Things Ltd.", 5000} - - //定义Men类型的变量i - var i Men - - //i能存储Student - i = mike - fmt.Println("This is Mike, a Student:") - i.SayHi() - i.Sing("November rain") - - //i也能存储Employee - i = tom - fmt.Println("This is tom, an Employee:") - i.SayHi() - i.Sing("Born to be wild") - - //定义了slice Men - fmt.Println("Let's use a slice of Men and see what happens") - x := make([]Men, 3) - //这三个都是不同类型的元素,但是他们实现了interface同一个接口 - x[0], x[1], x[2] = paul, sam, mike - - for _, value := range x{ - value.SayHi() - } +// Interface Men被Human,Student和Employee实现 +// 因为这三个类型都实现了这两个方法 +type Men interface { + SayHi() + Sing(lyrics string) +} + +func main() { + mike := Student{Human{"Mike", 25, "222-222-XXX"}, "MIT", 0.00} + paul := Student{Human{"Paul", 26, "111-222-XXX"}, "Harvard", 100} + sam := Employee{Human{"Sam", 36, "444-222-XXX"}, "Golang Inc.", 1000} + tom := Employee{Human{"Tom", 37, "222-444-XXX"}, "Things Ltd.", 5000} + + //定义Men类型的变量i + var i Men + + //i能存储Student + i = mike + fmt.Println("This is Mike, a Student:") + i.SayHi() + i.Sing("November rain") + + //i也能存储Employee + i = tom + fmt.Println("This is tom, an Employee:") + i.SayHi() + i.Sing("Born to be wild") + + //定义了slice Men + fmt.Println("Let's use a slice of Men and see what happens") + x := make([]Men, 3) + //这三个都是不同类型的元素,但是他们实现了interface同一个接口 + x[0], x[1], x[2] = paul, sam, mike + + for _, value := range x{ + value.SayHi() } +} ``` 通过上面的代码,你会发现interface就是一组抽象方法的集合,它必须由其他非interface类型实现,而不能自我实现, Go通过interface实现了duck-typing:即"当看到一只鸟走起来像鸭子、游泳起来像鸭子、叫起来也像鸭子,那么这只鸟就可以被称为鸭子"。 @@ -179,13 +179,13 @@ interface类型定义了一组方法,如果某个对象实现了某个接口 空interface(interface{})不包含任何的method,正因为如此,所有的类型都实现了空interface。空interface对于描述起不到任何的作用(因为它不包含任何的method),但是空interface在我们需要存储任意类型的数值的时候相当有用,因为它可以存储任意类型的数值。它有点类似于C语言的void*类型。 ```Go - // 定义a为空接口 - var a interface{} - var i int = 5 - s := "Hello world" - // a可以存储任意类型的数值 - a = i - a = s +// 定义a为空接口 +var a interface{} +var i int = 5 +s := "Hello world" +// a可以存储任意类型的数值 +a = i +a = s ``` 一个函数把interface{}作为参数,那么他可以接受任意类型的值作为参数,如果一个函数返回interface{},那么也就可以返回任意类型的值。是不是很有用啊! ### interface函数参数 @@ -194,41 +194,41 @@ interface的变量可以持有任意实现该interface类型的对象,这给 举个例子:fmt.Println是我们常用的一个函数,但是你是否注意到它可以接受任意类型的数据。打开fmt的源码文件,你会看到这样一个定义: ```Go - type Stringer interface { - String() string - } +type Stringer interface { + String() string +} ``` 也就是说,任何实现了String方法的类型都能作为参数被fmt.Println调用,让我们来试一试 ```Go - package main - import ( - "fmt" - "strconv" - ) +package main +import ( + "fmt" + "strconv" +) - type Human struct { - name string - age int - phone string - } +type Human struct { + name string + age int + phone string +} - // 通过这个方法 Human 实现了 fmt.Stringer - func (h Human) String() string { - return "❰"+h.name+" - "+strconv.Itoa(h.age)+" years - ✆ " +h.phone+"❱" - } +// 通过这个方法 Human 实现了 fmt.Stringer +func (h Human) String() string { + return "❰"+h.name+" - "+strconv.Itoa(h.age)+" years - ✆ " +h.phone+"❱" +} - func main() { - Bob := Human{"Bob", 39, "000-7777-XXX"} - fmt.Println("This Human is : ", Bob) - } +func main() { + Bob := Human{"Bob", 39, "000-7777-XXX"} + fmt.Println("This Human is : ", Bob) +} ``` 现在我们再回顾一下前面的Box示例,你会发现Color结构也定义了一个method:String。其实这也是实现了fmt.Stringer这个interface,即如果需要某个类型能被fmt包以特殊的格式输出,你就必须实现Stringer这个接口。如果没有实现这个接口,fmt将以默认的方式输出。 ```Go - //实现同样的功能 - fmt.Println("The biggest one is", boxes.BiggestsColor().String()) - fmt.Println("The biggest one is", boxes.BiggestsColor()) +//实现同样的功能 +fmt.Println("The biggest one is", boxes.BiggestsColor().String()) +fmt.Println("The biggest one is", boxes.BiggestsColor()) ``` 注:实现了error接口的对象(即实现了Error() string的对象),使用fmt输出时,会调用Error()方法,因此不必再定义String()方法了。 ### interface变量存储的类型 @@ -244,44 +244,44 @@ interface的变量可以持有任意实现该interface类型的对象,这给 让我们通过一个例子来更加深入的理解。 ```Go - package main + package main - import ( - "fmt" - "strconv" - ) + import ( + "fmt" + "strconv" + ) - type Element interface{} - type List [] Element + type Element interface{} + type List [] Element - type Person struct { - name string - age int - } + type Person struct { + name string + age int + } - //定义了String方法,实现了fmt.Stringer - func (p Person) String() string { - return "(name: " + p.name + " - age: "+strconv.Itoa(p.age)+ " years)" - } + //定义了String方法,实现了fmt.Stringer + func (p Person) String() string { + return "(name: " + p.name + " - age: "+strconv.Itoa(p.age)+ " years)" + } - func main() { - list := make(List, 3) - list[0] = 1 // an int - list[1] = "Hello" // a string - list[2] = Person{"Dennis", 70} + func main() { + list := make(List, 3) + list[0] = 1 // an int + list[1] = "Hello" // a string + list[2] = Person{"Dennis", 70} - for index, element := range list { - if value, ok := element.(int); ok { - fmt.Printf("list[%d] is an int and its value is %d\n", index, value) - } else if value, ok := element.(string); ok { - fmt.Printf("list[%d] is a string and its value is %s\n", index, value) - } else if value, ok := element.(Person); ok { - fmt.Printf("list[%d] is a Person and its value is %s\n", index, value) - } else { - fmt.Printf("list[%d] is of a different type\n", index) - } + for index, element := range list { + if value, ok := element.(int); ok { + fmt.Printf("list[%d] is an int and its value is %d\n", index, value) + } else if value, ok := element.(string); ok { + fmt.Printf("list[%d] is a string and its value is %s\n", index, value) + } else if value, ok := element.(Person); ok { + fmt.Printf("list[%d] is a Person and its value is %s\n", index, value) + } else { + fmt.Printf("list[%d] is of a different type\n", index) } } + } ``` 是不是很简单啊,同时你是否注意到了多个if里面,还记得我前面介绍流程时讲过,if里面允许初始化变量。 @@ -291,45 +291,45 @@ interface的变量可以持有任意实现该interface类型的对象,这给 最好的讲解就是代码例子,现在让我们重写上面的这个实现 ```Go - package main + package main - import ( - "fmt" - "strconv" - ) + import ( + "fmt" + "strconv" + ) - type Element interface{} - type List [] Element + type Element interface{} + type List [] Element - type Person struct { - name string - age int - } + type Person struct { + name string + age int + } - //打印 - func (p Person) String() string { - return "(name: " + p.name + " - age: "+strconv.Itoa(p.age)+ " years)" - } + //打印 + func (p Person) String() string { + return "(name: " + p.name + " - age: "+strconv.Itoa(p.age)+ " years)" + } - func main() { - list := make(List, 3) - list[0] = 1 //an int - list[1] = "Hello" //a string - list[2] = Person{"Dennis", 70} + func main() { + list := make(List, 3) + list[0] = 1 //an int + list[1] = "Hello" //a string + list[2] = Person{"Dennis", 70} - for index, element := range list{ - switch value := element.(type) { - case int: - fmt.Printf("list[%d] is an int and its value is %d\n", index, value) - case string: - fmt.Printf("list[%d] is a string and its value is %s\n", index, value) - case Person: - fmt.Printf("list[%d] is a Person and its value is %s\n", index, value) - default: - fmt.Println("list[%d] is of a different type", index) - } + for index, element := range list{ + switch value := element.(type) { + case int: + fmt.Printf("list[%d] is an int and its value is %d\n", index, value) + case string: + fmt.Printf("list[%d] is a string and its value is %s\n", index, value) + case Person: + fmt.Printf("list[%d] is a Person and its value is %s\n", index, value) + default: + fmt.Println("list[%d] is of a different type", index) } } + } ``` 这里有一点需要强调的是:`element.(type)`语法不能在switch外的任何逻辑里面使用,如果你要在switch外面判断一个类型就使用`comma-ok`。 @@ -339,33 +339,33 @@ Go里面真正吸引人的是它内置的逻辑语法,就像我们在学习Str 我们可以看到源码包container/heap里面有这样的一个定义 ```Go - type Interface interface { - sort.Interface //嵌入字段sort.Interface - Push(x interface{}) //a Push method to push elements into the heap - Pop() interface{} //a Pop elements that pops elements from the heap - } +type Interface interface { + sort.Interface //嵌入字段sort.Interface + Push(x interface{}) //a Push method to push elements into the heap + Pop() interface{} //a Pop elements that pops elements from the heap +} ``` 我们看到sort.Interface其实就是嵌入字段,把sort.Interface的所有method给隐式的包含进来了。也就是下面三个方法: ```Go - type Interface interface { - // Len is the number of elements in the collection. - Len() int - // Less returns whether the element with index i should sort - // before the element with index j. - Less(i, j int) bool - // Swap swaps the elements with indexes i and j. - Swap(i, j int) - } +type Interface interface { + // Len is the number of elements in the collection. + Len() int + // Less returns whether the element with index i should sort + // before the element with index j. + Less(i, j int) bool + // Swap swaps the elements with indexes i and j. + Swap(i, j int) +} ``` 另一个例子就是io包下面的 io.ReadWriter ,它包含了io包下面的Reader和Writer两个interface: ```Go - // io.ReadWriter - type ReadWriter interface { - Reader - Writer - } +// io.ReadWriter +type ReadWriter interface { + Reader + Writer +} ``` ### 反射 Go语言实现了反射,所谓反射就是能检查程序在运行时的状态。我们一般用到的包是reflect包。如何运用reflect包,官方的这篇文章详细的讲解了reflect包的实现原理,[laws of reflection](http://golang.org/doc/articles/laws_of_reflection.html) @@ -373,38 +373,38 @@ Go语言实现了反射,所谓反射就是能检查程序在运行时的状态 使用reflect一般分成三步,下面简要的讲解一下:要去反射是一个类型的值(这些值都实现了空interface),首先需要把它转化成reflect对象(reflect.Type或者reflect.Value,根据不同的情况调用不同的函数)。这两种获取方式如下: ```Go - t := reflect.TypeOf(i) //得到类型的元数据,通过t我们能获取类型定义里面的所有元素 - v := reflect.ValueOf(i) //得到实际的值,通过v我们获取存储在里面的值,还可以去改变值 +t := reflect.TypeOf(i) //得到类型的元数据,通过t我们能获取类型定义里面的所有元素 +v := reflect.ValueOf(i) //得到实际的值,通过v我们获取存储在里面的值,还可以去改变值 ``` 转化为reflect对象之后我们就可以进行一些操作了,也就是将reflect对象转化成相应的值,例如 ```Go - tag := t.Elem().Field(0).Tag //获取定义在struct里面的标签 - name := v.Elem().Field(0).String() //获取存储在第一个字段里面的值 +tag := t.Elem().Field(0).Tag //获取定义在struct里面的标签 +name := v.Elem().Field(0).String() //获取存储在第一个字段里面的值 ``` 获取反射值能返回相应的类型和数值 ```Go - var x float64 = 3.4 - v := reflect.ValueOf(x) - fmt.Println("type:", v.Type()) - fmt.Println("kind is float64:", v.Kind() == reflect.Float64) - fmt.Println("value:", v.Float()) +var x float64 = 3.4 +v := reflect.ValueOf(x) +fmt.Println("type:", v.Type()) +fmt.Println("kind is float64:", v.Kind() == reflect.Float64) +fmt.Println("value:", v.Float()) ``` 最后,反射的话,那么反射的字段必须是可修改的,我们前面学习过传值和传引用,这个里面也是一样的道理。反射的字段必须是可读写的意思是,如果下面这样写,那么会发生错误 ```Go - var x float64 = 3.4 - v := reflect.ValueOf(x) - v.SetFloat(7.1) +var x float64 = 3.4 +v := reflect.ValueOf(x) +v.SetFloat(7.1) ``` 如果要修改相应的值,必须这样写 ```Go - var x float64 = 3.4 - p := reflect.ValueOf(&x) - v := p.Elem() - v.SetFloat(7.1) +var x float64 = 3.4 +p := reflect.ValueOf(&x) +v := p.Elem() +v.SetFloat(7.1) ``` 上面只是对反射的简单介绍,更深入的理解还需要自己在编程中不断的实践。