Go -- 接口

type Programmer interface {
    writeHelloWorld() string
}

// 不需要关键字：implements
type GoProgrammer struct {
}

// Duck Type式接口，与Programmer里面的方法签名完全一致
func (p *GoProgrammer) writeHelloWorld() string {
    return "fmt.Println(\"Hello World\")"
}

func TestInterface(t *testing.T) {
    var p Programmer
    p = new(GoProgrammer)
    t.Log(p.writeHelloWorld()) // fmt.Println("Hello World")
}

func TestInterfaceVar(t *testing.T) {
    var programmer Programmer = &GoProgrammer{}
    t.Logf("%T", programmer) // *interface_test.GoProgrammer
}

// 自定义类型（别名）
type IntConvert func(op int) int

func timeSpent(inner IntConvert) IntConvert {
    return func(op int) int {
    	start := time.Now()
    	ret := inner(op)
    	fmt.Println("time spent : ", time.Since(start).Seconds())
    	return ret
    }
}

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

func TestFuncAsParam(t *testing.T) {
    f := timeSpent(slowFunc)
    t.Log(f(10))
}