select与switch的区别 select与switch的区别

No.1 Select: select只能用于channel的操作，发送或接受数据，如果select有多个分支满足条件，他的特点是->随机选取其中一个满足条件的分支。
官方解释如下：

If multiple cases can proceed, a uniform pseudo-random choice is made to decide which single communication will execute.

下面是Concrete Example:

package mainimport ( "fmt" "time" )func main() { c1 := make(chan string) c2 := make(chan string) go func() { time.Sleep(time.Second * 1) c1 <- "one" }() go func() { time.Sleep(time.Second * 1) c2 <- "two" }()select { case msg1 := <-c1: fmt.Println("msg1 received is:", msg1) case msg2 := <-c2: fmt.Println("msg2 received is:", msg2) }}

虽然代码中select中2个分支的条件都是满足的，但是他不像switch那样按顺序。大家可以吧代码复制了自己测试下。
下面来看看我自己测试个6个结果：

msg1 received is: one msg2 received is: two msg2 received is: two msg1 received is: one msg2 received is: two msg1 received is: one

No.2 Switch: 【select与switch的区别】switch分支是按顺序执行的，这点和select不同，可以为各种类型进行分支操作这一点又与select不同，还可以用来判断类型。
下面是Concrete Example:

package mainimport "fmt" import "time"func main() { i := 2 fmt.Print("Write ", i, " as ") switch i { case 1: fmt.Println("one") case 2: fmt.Println("two") case 3: fmt.Println("three") } switch time.Now().Weekday() { case time.Saturday, time.Sunday: fmt.Println("It's the weekend") default: fmt.Println("It's a weekday") } t := time.Now() switch { case t.Hour() < 12: fmt.Println("It's before noon") default: fmt.Println("It's after noon") } 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") }

下面的输出结果一目了然我不多解释：