Decorator模式：打造可扩展、灵活的应用

2023-09-23 16:25:47

Decorator模式的优点

Decorator模式具有以下优点：

可扩展性： Decorator模式可以轻松地为现有对象添加新功能，而无需修改其源代码。
灵活性： Decorator模式可以动态地为对象添加功能，而无需重新编译代码。
解耦性： Decorator模式可以将对象的实现与它的功能分离，使代码更易于理解和维护。

Decorator模式的实现

在Java中，Decorator模式可以通过实现java.io.Serializable接口来实现。在Python中，Decorator模式可以通过使用@符号来实现。

Java中的Decorator模式

public interface Shape {
  void draw();
}

public class Rectangle implements Shape {
  @Override
  public void draw() {
    System.out.println("Drawing a rectangle");
  }
}

public class Circle implements Shape {
  @Override
  public void draw() {
    System.out.println("Drawing a circle");
  }
}

public class ShapeDecorator implements Shape {
  private Shape shape;

  public ShapeDecorator(Shape shape) {
    this.shape = shape;
  }

  @Override
  public void draw() {
    shape.draw();
  }
}

public class RedShapeDecorator extends ShapeDecorator {
  public RedShapeDecorator(Shape shape) {
    super(shape);
  }

  @Override
  public void draw() {
    shape.draw();
    System.out.println("Drawing a red shape");
  }
}

public class GreenShapeDecorator extends ShapeDecorator {
  public GreenShapeDecorator(Shape shape) {
    super(shape);
  }

  @Override
  public void draw() {
    shape.draw();
    System.out.println("Drawing a green shape");
  }
}

public class Main {
  public static void main(String[] args) {
    Shape rectangle = new Rectangle();
    Shape circle = new Circle();

    Shape redRectangle = new RedShapeDecorator(rectangle);
    Shape greenCircle = new GreenShapeDecorator(circle);

    redRectangle.draw();
    greenCircle.draw();
  }
}

Python中的Decorator模式

from functools import wraps

def shape(func):
  @wraps(func)
  def wrapper(*args, **kwargs):
    print("Drawing a shape")
    func(*args, **kwargs)
  return wrapper

def rectangle(func):
  @wraps(func)
  def wrapper(*args, **kwargs):
    print("Drawing a rectangle")
    func(*args, **kwargs)
  return wrapper

def circle(func):
  @wraps(func)
  def wrapper(*args, **kwargs):
    print("Drawing a circle")
    func(*args, **kwargs)
  return wrapper

@shape
def draw_rectangle():
  pass

@shape
@rectangle
def draw_red_rectangle():
  pass

@shape
@circle
def draw_green_circle():
  pass

draw_rectangle()
draw_red_rectangle()
draw_green_circle()