golang闭包的坑

1. 循环内goroutine使用闭包

func main() {
	s := []string{"a", "b", "c"}
	for _, v := range s {
		go func() {
			fmt.Println(v)
		}()
	}

	time.Sleep(time.Second)
}


// c c c

改进:

func main() {                
    s := []string{"a", "b", "c"}                             
    for _, v := range s { 
        go func(v string) {
            fmt.Println(v)
        }(v)      
    }                                                                            
}
// a b c


func main() {
	s := []string{"a", "b", "c"}
	for _, v := range s {
		vv := v
		go func() {
			fmt.Println(vv)
		}()
	}

	time.Sleep(time.Second)
}
// a b c

2. 循环内闭包函数列表

func test() []func() {
    var s []func()

    for i := 0; i < 3; i++ {
        s = append(s, func() {  
            fmt.Println(&i, i)
        })
    }

    return s    
}
func main() {
    for _, f := range test() { 
        f()   
    }
}

/*
0x1400001a0f8 3
0x1400001a0f8 3
0x1400001a0f8 3
*/

改进:

func test() []func() {
    var s []func()
    
    for i := 0; i < 3; i++ {
        x := i                 
        s = append(s, func() {
            fmt.Println(&x, x)
        })
    }

    return s
}
func main() {
    for _, f := range test() {
        f()
    }
}

/*
0x1400001a0f8 0
0x1400001a100 1
0x1400001a108 2
*/

3. defer延迟调用闭包

func main() {
	x, y := 1, 2

	defer func(x int) {
		fmt.Println("defer", "x", x, "y", y)  // y是闭包引用
	}(x)

	x += 100
	y += 100
	fmt.Println("main", "x", x, "y", y)
}



/*
main x 101 y 102
defer x 1 y 102
*/