[Go语言]从Docker源码学习Go——Interfaces

type Namer interface {
    Method1(param_list) return_type
    Method2(param_list) return_type
    ...
}

type ReadWrite interface {
    Read(b Buffer) bool
    Write(b Buffer) bool
}

type Lock interface {
    Lock()
    Unlock()
}

type File interface {
    ReadWrite
    Lock
    Close()
}

v := varI.(T)
//varI must be an interface variable.

package lemon

type Shaper interface {
    Area() float32
}
type Square struct {
    Side float32
}

func (sq *Square) Area() float32 {
    return sq.Side * sq.Side
}

//use in main func.
func showInterfaceUsage() {
    sq1 := new(lemon.Square)
    sq1.Side = 5
    var areaIntf lemon.Shaper
    areaIntf = sq1

    if v, ok := areaIntf.(*lemon.Square); ok {
        fmt.Printf("The square has area: %f\n", v.Area())
    }
}

    switch areaIntf.(type) {
    case *lemon.Square:
        fmt.Printf("The square area is %f\n", areaIntf.Area())
    default:
        fmt.Printf("The default type")
    }