GO_函数_07

落日映苍穹つ 2024-04-07 10:57 10阅读 0赞

## 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