桥接模式 Bridge Pattern

介绍

• 用于把抽象化与实现化解耦
• 使得二者可以独立变化

示例

我们要画图形

涉及到颜色和形状，可能会这样画👇

class ColorShape {
  yellowCircle() {
    console.log(`draw yellow circle`)
  }
  greenCircle() {
    console.log(`draw green circle`)
  }
  yellowTriangle() {
    console.log(`draw yellow Triangle`)
  }
  greenTriangle() {
    console.log(`draw green Triangle`)
  }
}

const draw = new ColorShape();
draw.yellowCircle()
draw.greenCircle()
draw.yellowTriangle()
draw.greenTriangle()

如果我们想把颜色和图形分离开，可以这样👇🏻

class Color {
  constructor(colorName) {
    this.colorName = colorName
  }
}

class Shape {
  constructor(shapeName) {
    this.shapeName = shapeName
  }
}

class Draw {
  constructor(color, shape) {
    this.color = color
    this.shape = shape
  }
  draw() {
    console.log(this.color.colorName, this.shape.shapeName)
  }
}

const yellow = new Color('yellow')
const green = new Color('green')
const circle = new Shape('circle')
const triangle = new Shape('triangle')
const yellowCircle = new Draw(yellow, circle)
yellowCircle.draw()
const greenTriangle = new Draw(green, triangle)
greenTriangle.draw()

如果以后颜色有九九八十一种的话，第一种方式我们就要写…😥老长，并且每次都需要修改 ColorShape 类。利用桥接模式后复杂性就会大大降低，可灵活组合。

class Color {
  constructor(colorName) {
    this.colorName = colorName
  }
}

class Shape {
  constructor(shapeName) {
    this.shapeName = shapeName
  }
}

class Draw {
  constructor(color, shape) {
    this.color = new Color(color)
    this.shape = new Shape(shape)
  }
  draw() {
    console.log(this.color.colorName, this.shape.shapeName)
  }

  getColor() {
    console.log(this.color.colorName)
  }

  getShape() {
    console.log(this.shape.shapeName)
  }
}

const yellowCircle = new Draw('yellow', 'circle')
yellowCircle.draw()
const greenTriangle = new Draw('green', 'triangle')
greenTriangle.draw()

设计原则验证

• 抽象和实现分离，解耦
• 符合开放封闭原则