Go-select和switch的使用区别

Go-select和switch的使用区别

package main

import (
    "fmt"
    "time"
)

func main() {
    i := 2
    fmt.Print("Write ", i, " as ") //Write 2 as two
    switch i {
    case 1:
        fmt.Println("one")
    case 2:
        fmt.Println("two")
    case 3:
        fmt.Println("three")
    }

    switch time.Now().Weekday() { //It's a weekday
    case time.Saturday, time.Sunday:
        fmt.Println("It's the weekend")
    default:
        fmt.Println("It's a weekday")
    }

    t := time.Now() //It's after noon
    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)  //I'm a bool
    whatAmI(1)     //I'm an int
    whatAmI("hey") //Don't know type string
}

//select里面的case都满足了，则随机选择一个执行
func main02() {
    c1 := make(chan string)
    c2 := make(chan string)
    go func() {
        time.Sleep(time.Second * 1)
        c1 <- "one"
    }()
    go func() {
        time.Sleep(time.Second * 2)
        c2 <- "two"
    }()
    for i := 0; i < 2; i++ {
        select {
        case msg1 := <-c1:
            fmt.Println("received", msg1)
        case msg2 := <-c2:
            fmt.Println("received", msg2)
        }
    }
}

func main01() {
    var c1, c2, c3 chan int
    var i1, i2 int

    c1 <- 666

    select {
    case i1 = <-c1:
        fmt.Printf("received %d from c1\n", i1)
    case c2 <- i2:
        fmt.Printf("sent %d to c2\n", i2)
    case i3, ok := <-c3: // same as: i3, ok := <-c3
        if ok {
            fmt.Printf("received %d from c3\n", i3)
        } else {
            fmt.Printf("c3 is closed\n")
        }
    default:
        fmt.Printf("no communication\n")
    }
}