键入 switch 语句

一个简单的类型开关：

// assuming x is an expression of type interface{}
switch t := x.(type) {
case nil:
    // x is nil
    // t will be type interface{}
case int: 
    // underlying type of x is int
    // t will be int in this case as well
case string:
    // underlying type of x is string
    // t will be string in this case as well
case float, bool:
    // underlying type of x is either float or bool
    // since we don't know which, t is of type interface{} in this case
default:
    // underlying type of x was not any of the types tested for
    // t is interface{} in this type
}

你可以测试任何类型，包括 error，用户定义的类型，接口类型和函数类型：

switch t := x.(type) {
case error:
    log.Fatal(t)
case myType:
    fmt.Println(myType.message)
case myInterface:
    t.MyInterfaceMethod()
case func(string) bool:
    if t("Hello world?") {
        fmt.Println("Hello world!")
    }
}