gobyexample-switch

来源：https://github.com/xg-wang/gobyexample/tree/master/examples

package main

import (
    "fmt"
    "time"
)

func main() {

    //一个基本的 `switch`
    i := 2
    fmt.Print("write ", i, " as ")
    switch i {
    case 1:
        fmt.Println("one")
    case 2:
        fmt.Println("two")
    case 3:
        fmt.Println("three")
    }

    //在同一个`case`语句终稿，你可以使用逗号来分隔多个表达式。在这个例子中，我们还使用了可选的
    //`default`分支
    switch time.Now().Weekday() {
    case time.Saturday, time.Sunday:
        fmt.Println("It's the weekend")
    default:
        fmt.Println("It's  a weekday")
    }

    //不带表达式的`switch` 是实现if/else逻辑的另一种方式。这里还展示了`case`表达式也可以不使用常量
    t := time.Now()
    switch {
    case t.Hour() < 12:
        fmt.Println("It's before noon")
    default:
        fmt.Println("It's after noon")
    }

    //类型开关(`type switch`)比较类型而非值。可以用来发现一个接口值的类型。在这个例子中，变量`t`在每个分支中会有相应的类型
    whatAmI := func(i interface{}) {
        switch t := i.(type) {
        case bool:
            fmt.Println("I'm a bool")
        case int:
            fmt.Println("I'm an int")
        default:
            fmt.Printf("Don't know type %T\n", t)
        }
    }

    whatAmI(true)
    whatAmI(1)
    whatAmI("hey")
}

输出：

$ go run switch.go
Write 2 as two
It's a weekday
It's after noon
I'm a bool
I'm an int
Don't know type string