Go interface{}, type assertion

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In Golang interface{} can be used to pass a variable of any type to a function, but used inside a function, the type of the variable is interface{}, also known as an empty interface type

For example, we define a function, output a string, but the argument is interface{} type

func echoString(content interface{}) {    fmt.Println(content )}

When we call echoString("输出字符串") the method, we get content an error because it's a interface{} type, not a string type.

The conversion of an interface type to a normal type is called a type assertion (run-time determination)

For the above call, you can modify the method byechoString

func echoString(content interface{}) {    result, _ := content.(string)  //通过断言实现类型转换    fmt.Println(result)}

This time there will be a potential threat, if we give the method is the int type, then we 断言 will be error, this time we need to perfect the code

func echoString(content interface{}) {    result, err := content.(string)      if err != nil {  // 断言失败        fmt.Println(err .Error())  // 输出失败原因        return    }    fmt.Println(result)}

Operations of different types of variables must be explicitly type-cast, and the result may be error-