原始装饰器的实际缺点

Question

受Decorator 模式的启发，但确信该模式的要点可以以较低的复杂性实现，我制作了两个快速的 sn-ps，分别用 C++11 和 Java 编写。

装饰器.cpp：

#include <iostream>
#include <string>

using namespace std;

class Box {

public:
    virtual string getDescription()
    {
        return "A box";
    }
};

class BoxDecorator : public Box {
    Box* wrapee;

public:
    BoxDecorator(Box* box)
    {
        wrapee = box;
    }
    string getDescription()
    {
        return wrapee->getDescription();
    }
};

class RedBox : public BoxDecorator {

public:
    RedBox(Box* box)
        : BoxDecorator(box)
    {
    }

    string getDescription()
    {
        return BoxDecorator::getDescription() + ", red-colored";
    }
};

class BigBox : public BoxDecorator {

public:
    BigBox(Box* box)
        : BoxDecorator(box)
    {
    }

    string getDescription()
    {
        return BoxDecorator::getDescription() + ", big-sized";
    }
};

class StripedBox : public BoxDecorator {

public:
    StripedBox(Box* box)
        : BoxDecorator(box)
    {
    }

    string getDescription()
    {
        return BoxDecorator::getDescription() + ", with several stripes around it";
    }
};

int main()
{
    Box* sampleBox = new StripedBox(new RedBox(new BigBox(new Box())));
    cout << sampleBox->getDescription() << endl;
}

装饰器.java：

class Box {

 public Box() {

 }

 public String getDescription() {
  return "A box";
 }

}

class BoxDecorator extends Box {

 Box boxToBeDecorated;

 public BoxDecorator(Box box) {
  boxToBeDecorated = box;
 }

 public String getDescription() {
  return boxToBeDecorated.getDescription();
 }


}

class RedBox extends BoxDecorator {

 public RedBox(Box box) {
  super(box);
 }

 public String getDescription() {
  return super.getDescription() + ", red-colored";
 }
}

class BigBox extends BoxDecorator {

 public BigBox(Box box) {
  super(box);
 }

 public String getDescription() {
  return super.getDescription() + ", big-sized";
 }
}

class StripedBox extends BoxDecorator {

 public StripedBox(Box box) {
  super(box);
 }

 public String getDescription() {
  return super.getDescription() + ", with several stripes around it";
 }
}

public class Decorator {

 public static void main(String[] args) {

  Box sampleBox = new StripedBox(new RedBox(new BigBox(new Box())));
  System.out.println(sampleBox.getDescription());

 }
}

两者都在生成有效的“一个盒子，大号，红色，周围有几条条纹”输出。因此，以 Java 为例，并不是语言的复杂性迫使我们to use interfaces or abstract classes。

那么，这些被剥离的“装饰器”有哪些实际缺点？

Answer 1

在这里你继承了 Box 的实现。这需要内存，可能会导致问题（例如，构造函数可能有副作用）。没有继承Box的理由。此外，如果使用继承，装饰器链的可能组合数量会呈指数增长。