80 lines
1.8 KiB
Dart
80 lines
1.8 KiB
Dart
/**
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装饰器模式（Decorator Pattern）
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意图：动态地给一个对象添加一些额外的职责。就增加功能来说，装饰器模式相比生成子类更为灵活。
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主要解决：一般的，我们为了扩展一个类经常使用继承方式实现，由于继承为类引入静态特征，并且随着扩展功能的增多，子类会很膨胀。
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何时使用：在不想增加很多子类的情况下扩展类。
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如何解决：将具体功能职责划分，同时继承装饰者模式。
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*/
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main(List<String> args) {
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Shape circle = new Circle();
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Shape redCircle = new RedShapeDecorator(new Circle());
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Shape redRectangle = new RedShapeDecorator(new Rectangle());
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print("Circle with normal border");
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circle.draw();
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print("\nCircle of red border");
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redCircle.draw();
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print("\nRectangle of red border");
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redRectangle.draw();
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}
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//////////////////////////////////////////////////////////////////
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///
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/// 创建一个接口
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///
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abstract class Shape {
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void draw();
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}
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///
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/// 创建实现接口的实体类
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///
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class Rectangle implements Shape {
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@override
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void draw() {
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print("Shape: Rectangle");
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}
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}
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class Circle implements Shape {
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@override
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void draw() {
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print("Shape: Circle");
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}
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}
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///
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/// 创建实现了 Shape 接口的抽象装饰类
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///
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abstract class ShapeDecorator implements Shape {
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Shape _decoratedShape;
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ShapeDecorator(this._decoratedShape);
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void draw() {
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_decoratedShape.draw();
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}
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}
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///
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/// 创建扩展了 ShapeDecorator 类的实体装饰类
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///
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class RedShapeDecorator extends ShapeDecorator {
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RedShapeDecorator(Shape decoratedShape) : super(decoratedShape);
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@override
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void draw() {
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_decoratedShape.draw();
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setRedBorder(_decoratedShape);
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}
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void setRedBorder(Shape decoratedShape) {
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print("Border Color: Red");
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}
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}
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