2.4 装饰器模式

代码实现
下面是一个简单的画画的例子，默认的 Square  只有基础的画画功能， ColorSquare  为他加上了颜色

package decorator

// IDraw IDraw
type IDraw interface {
    Draw() string
}

// Square 正方形
type Square struct {}

// Draw Draw
func(s Square) Draw() string {
    return "this is a square"
}

// ColorSquare 有颜色的正方形
type ColorSquare struct {
    square IDraw
    color string
}

// NewColorSquare NewColorSquare
func NewColorSquare(square IDraw, color string) ColorSquare {
    return ColorSquare {
        color: color,
        square: square
    }
}

// Draw Draw
func(c ColorSquare) Draw() string {
    return c.square.Draw() + ", color is " + c.color
}

func TestColorSquare_Draw(t * testing.T) {
    sq: = Square {}
    csq: = NewColorSquare(sq, "red")
    got: = csq.Draw()
    assert.Equal(t, "this is a square, color is red", got)
}