GO_函数_07

函数

1. 可以有多个返回值
2. 所有参数都是值传递： slice， map， channel 会有传引用的错觉
3. 函数可以作为变量量的值
4. 函数可以作为参数和返回值

函数：可变参数及 defer

可变参数

func sum(ops ...int) int {
    
    
s := 0
for _, op := range ops {
    
    
s += op
}
return s
}

defer 函数

func TestDefer(t *testing.T) {
    
    
defer func() {
    
    
t.Log("Clear resources")
}()
t.Log("Started")
panic("Fatal error”) //defer仍会执行
}

demo

// 返回俩个随机数
func returnMultiValues() (int, int) {
    
    
	return rand.Intn(15), rand.Intn(30)
}

// 计算函数操作的时长
func timeSpent(inner func(op int) int) func(op int) int {
    
    
	return func(n int) int {
    
    
		start := time.Now()
		ret := inner(n)
		fmt.Println("time spent:", time.Since(start).Seconds())
		return ret
	}
}

func slowFun(op int) int {
    
    
	time.Sleep(time.Second * 1)
	return op
}

func TestFn(t *testing.T) {
    
    
	a, b := returnMultiValues()
	t.Log(a, b)
	timeSF := timeSpent(slowFun)
	t.Log(timeSF(10))
}


func Sum(ops ...int) int {
    
    
	ret := 0
	for _, op := range ops {
    
    
		ret += op
	}
	return ret
}

func TestVarParam(t *testing.T) {
    
    
	t.Log(Sum(1, 2, 3, 4))
	t.Log(Sum(1, 2, 3, 4, 5))
}

func Clear() {
    
    
	fmt.Println("Clear resources.")
}

func TestDefer(t *testing.T) {
    
    
	defer Clear()
	fmt.Println("Start")
	//panic("err")
}

demo1

func TestFn(t *testing.T) {
    
    
	a, b := returnMultiValues()
	t.Log(a, b)
	timeSF := timeSpent(slowFun)
	t.Log(timeSF(10))
}

result1:

=== RUN   TestFn
    fun_test.go:32: 11 27
time spent: 1.0093736
    fun_test.go:34: 10
--- PASS: TestFn (1.01s)
PASS

demo2

func TestVarParam(t *testing.T) {
    
    
	t.Log(Sum(1, 2, 3, 4))
	t.Log(Sum(1, 2, 3, 4, 5))
}

result:

=== RUN   TestVarParam
    fun_test.go:47: 10
    fun_test.go:48: 15
--- PASS: TestVarParam (0.00s)
PASS

demo3

func TestDefer(t *testing.T) {
    
    
	defer Clear()
	fmt.Println("Start")
	//panic("err")
}

result:

=== RUN   TestDefer
Start
Clear resources.
--- PASS: TestDefer (0.00s)
PASS