go_教程_02

• 使用包
• error
• 并发--Goroutines

使用包

package main
import (
    "errors"
    "fmt"
)

error

//error
func f1(arg int) (int, error) {
    if arg == 42 {
        return -1, errors.New("can't work with 42")
    }
    return arg + 3 , nil
}
// 自定义的error
type argError struct {
    arg int
    prob string
}
/**
自定义的错误，就是实现系统的内置的这个接口
type error interface {
    Error() string
}
 */
func (e argError) Error() string { //实现接口
    return fmt.Sprintf("%d - %s", e.arg, e.prob)
}

func f2(arg int) (int,error) {
    if arg == 42 {
        return -1, argError{arg,"can't work with it"}
    }
    return arg + 3, nil
}

func main(){
    for _,i := range []int{7,42} {
        if r,e := f1(i); e != nil {
            fmt.Println("f1 failed: ", e)
        }else{
            fmt.Println("f1 worked: ", r)
        }
    }

    for _,i := range []int{7,42} {
        if r,e := f2(i); e != nil {
            fmt.Println("f2 failed: ", e)
        }else {
            fmt.Println("f2 worked: ", r)
        }
    }

    fmt.Println("=========")
    _, e := f2(42)
    /**
    把实现类输入error,获得属性
    e.(argError)
     */
    if ae,ok := e.(argError); ok {
        fmt.Println("ok: ", ok)
        fmt.Println("arg: ", ae.arg)
        fmt.Println("prob: ", ae.prob)
    }

}

并发--Goroutines

// Goroutines
func f(from string){
    for i := 0; i < 50; i++ {
        fmt.Println(from,i)
    }
}
func main(){
    fmt.Println("-----goroutines------")
    f("direct")
    // 使用go下面两个方法在不同线程异步执行
    go f("goroutine")
    go func(msg string) {
        fmt.Println(msg)
    }("going")

    fmt.Scanln()
    fmt.Println("done")
}