The interface of Go language

Interface theory

• An interface is a collection of one or more method signatures
• As long as a type has all the method signatures for that interface, that interface is implemented, without showing which interface the declaration implements, which is called Structural Typing
• Interfaces are only method declarations, no implementations, no data fields
• Interfaces can be embedded anonymously in other interfaces, or embedded in a structure
• When an object is assigned to an interface, a copy occurs, and the interface stores a pointer to the replica that cannot modify the state of the replica or retrieve the pointer
• The interface is equal to nil only if the interface stores both the type and the object are nil
• Interface calls do not automatically convert receiver
• Interface also supports anonymous field methods
• Interfaces can also be implemented to resemble the polymorphism in OOP
• An empty interface can be used as a container for task type data

Example 1, creating an interface

// interface 接口  练习//实现接口的原则就是//实现了它定义的方法，就默认是实现了接口package mainimport "fmt"//声明一个接口type USB interface {    //声明方法Name,  并设置 返回值类型string    Name() string    //声明方法Connect方法，无返回值    Connect()}//声明一个类型，在Go语言中，对应的就是struct类型type PhoneConnector struct {    //声明一个私有属性    name string}//---------------------声明完Name,Connector方法后，就是实现了USB接口了---------------------------//使用receiver，将类型跟方法进行绑定func (pc PhoneConnector)Name() string{    return pc.name}func (pc PhoneConnector)Connector()  {    fmt.Println("connected:\t", pc.name)}//--------------------------------------------------------------------------------------func main() {    a := PhoneConnector{"apple"}    fmt.Println("Name:\t", a.Name())    a.Connector()}

2. Nesting exercises between interfaces

Interface nested Practice Test Package Mainimport "FMT"//define an empty interface//In this case, all classes, the default implementation of this interface, because it does not have a method//definition of the Null interface, it is equivalent to define an object, the highest level/ /is its subclass, there is no limit to the type Nullempty interface {}//defines a parent interface type HOME Interface {//This interface, only one method Name () string}//is defined Port, which is equivalent to a sub-interface of type MyHome interface {Show () string//So nested an interface home}//declares a struct type beijinghome struct {name string}//-----------Start Creating Method-----Func (Info beijinghome) Show () {fmt.    Println ("Show ()--->info.name:\t", info.name)}func (info beijinghome) name () string{return Info.name}func main () { A: = beijinghome{"Yihuyuan"} fmt. Println ("Name:\t", A.name ()) a.show ()//------The following is a demonstration of the problem of---reproductions mentioned in the above theory----b: = a b.name = "Lenovo"//modified and not modified The value of a in B.show () Disconnect (a) Disconnect2 (a)}//design a simple Type assertion func Disconnect (home home) {if pc, OK: = home. Beijinghome); ok{FMT. Println ("Disconnected:\t", Pc.name) return} FMT. Println ("Unknown decive.")} Design a simple type assertion//incoming parameter, yes, NULL interface//Actually, for incoming parameters, there is no limit to the FuncDisconnect2 (Home interface{}) {///to the Disconnect () method, the transformation,//Because, the incoming parameter is the top level, equivalent to the Java object, there is no restriction//type, you need to judge the switch V: = home. (type) {Case Beijinghome:fmt. Println ("Disconnected:\t", V.name) default:fmt.    Println ("Unknown decive.") }}

3. Conversion between different interfaces

//不同接口之间的转换，类似于Java中的向上转型，或者向下转型//就是说，有两个接口A， B//其中，A接口里，嵌入了B//那么A接口可以转换成B接口，但是，B接口不能转换成A接口，因为//A接口里，可能包含B接口里没有的方法//也就是说，多的可以向少的转换，反之不可。package mainimport "fmt"type USB2 interface {    Name() string    Connecter}type Connecter interface {    Connect()}type PcConnecter struct {    name string}func (pcConnecter PcConnecter)Name() string {    return pcConnecter.name}func(pcConnecter PcConnecter)Connect() {    fmt.Println("Connected:\t", pcConnecter.name)}func main() {    pc := PcConnecter{"appleConnector"}    var a Connecter    //将USE2 类型，强制 转换成了Connecter类型    a = Connecter(pc)    a.Connect()    //------验证----只有当接口存储的类型和对象都为nil时，接口才等于nil    //声明一个空接口, 也没有赋值，就是nil    var aa interface{}    fmt.Println( aa == nil)  // aa 本身就是一个nil,啥也没存    //变量p， 是一个指向int类型的指针    //直接初始化为nil    var p *int = nil    aa = p //aa 指向p    fmt.Println( aa == nil)}

The interface of Go language