c++设计模式之装饰器模式

视频地址：

https://www.ixigua.com/6804249883344634380?id=6803643043019751947

文档整理地址：

http://t.csdn.cn/PwSdq

装饰器模式样例类图：

 

 

 代码样例：

//业务操作
class Stream {
public:
    virtual char Read(int number) = 0;
    virtual void Seek(int position) = 0;
    virtual void Write(char data) = 0;

    virtual ~Stream() {}
};

//主体类
class FileStream : public Stream {
public:
    virtual char Read(int number) {
        //读文件流
    }
    virtual void Seek(int position) {
        //定位文件流
    }
    virtual void Write(char data) {
        //写文件流
    }

};

class NetworkStream :public Stream {
public:
    virtual char Read(int number) {
        //读网络流
    }
    virtual void Seek(int position) {
        //定位网络流
    }
    virtual void Write(char data) {
        //写网络流
    }

};

class MemoryStream :public Stream {
public:
    virtual char Read(int number) {
        //读内存流
    }
    virtual void Seek(int position) {
        //定位内存流
    }
    virtual void Write(char data) {
        //写内存流
    }

};

//扩展操作
class CryptoFileStream :public FileStream {
public:
    virtual char Read(int number) {

        //额外的加密操作...
        FileStream::Read(number);//读文件流

    }
    virtual void Seek(int position) {
        //额外的加密操作...
        FileStream::Seek(position);//定位文件流
        //额外的加密操作...
    }
    virtual void Write(byte data) {
        //额外的加密操作...
        FileStream::Write(data);//写文件流
        //额外的加密操作...
    }
};

class CryptoNetworkStream :  public NetworkStream{
public:
    virtual char Read(int number) {

        //额外的加密操作...
        NetworkStream::Read(number);//读网络流
    }
    virtual void Seek(int position) {
        //额外的加密操作...
        NetworkStream::Seek(position);//定位网络流
        //额外的加密操作...
    }
    virtual void Write(byte data) {
        //额外的加密操作...
        NetworkStream::Write(data);//写网络流
        //额外的加密操作...
    }
};

class CryptoMemoryStream : public MemoryStream {
public:
    virtual char Read(int number) {

        //额外的加密操作...
        MemoryStream::Read(number);//读内存流
    }
    virtual void Seek(int position) {
        //额外的加密操作...
        MemoryStream::Seek(position);//定位内存流
        //额外的加密操作...
    }
    virtual void Write(byte data) {
        //额外的加密操作...
        MemoryStream::Write(data);//写内存流
        //额外的加密操作...
    }
};

class BufferedFileStream : public FileStream {
    //...
};

class BufferedNetworkStream : public NetworkStream {
    //...
};

class BufferedMemoryStream : public MemoryStream {
    //...
};



class CryptoBufferedFileStream :public FileStream {
public:
    virtual char Read(int number) {

        //额外的加密操作...
        //额外的缓冲操作...
        FileStream::Read(number);//读文件流
    }
    virtual void Seek(int position) {
        //额外的加密操作...
        //额外的缓冲操作...
        FileStream::Seek(position);//定位文件流
        //额外的加密操作...
        //额外的缓冲操作...
    }
    virtual void Write(byte data) {
        //额外的加密操作...
        //额外的缓冲操作...
        FileStream::Write(data);//写文件流
        //额外的加密操作...
        //额外的缓冲操作...
    }
};

void Process() {

    //编译时装配
    CryptoFileStream* fs1 = new CryptoFileStream();

    BufferedFileStream* fs2 = new BufferedFileStream();

    CryptoBufferedFileStream* fs3 = new CryptoBufferedFileStream();
}

 

类的规模：1+n+n*m!/2，原因是对类的继承不良使用

重构后类图：

 

 重构后代码：

//业务操作
class Stream {
public:
    virtual char Read(int number) = 0;
    virtual void Seek(int position) = 0;
    virtual void Write(char data) = 0;
    virtual ~Stream() {}
};
//主体类
class FileStream : public Stream {
public:
    virtual char Read(int number) {
        //读文件流
    }
    virtual void Seek(int position) {
        //定位文件流
    }
    virtual void Write(char data) {
        //写文件流
    }

};

class NetworkStream :public Stream {
public:
    virtual char Read(int number) {
        //读网络流
    }
    virtual void Seek(int position) {
        //定位网络流
    }
    virtual void Write(char data) {
        //写网络流
    }

};

class MemoryStream :public Stream {
public:
    virtual char Read(int number) {
        //读内存流
    }
    virtual void Seek(int position) {
        //定位内存流
    }
    virtual void Write(char data) {
        //写内存流
    }

};
//扩展操作
//中间装饰类
class DecoratorStream : public Stream {
protected:
    Stream* stream;//...

    DecoratorStream(Stream* stm) :stream(stm) {

    }

};

class CryptoStream : public DecoratorStream {


public:
    CryptoStream(Stream* stm) :DecoratorStream(stm) {

    }

    virtual char Read(int number) {

        //额外的加密操作...
        stream->Read(number);//读文件流
    }
    virtual void Seek(int position) {
        //额外的加密操作...
        Stream::Seek(position);//定位文件流
        //额外的加密操作...
    }
    virtual void Write(byte data) {
        //额外的加密操作...
        Stream::Write(data);//写文件流
        //额外的加密操作...
    }
};

class BufferedStream : public DecoratorStream {

    Stream* stream;//...

public:
    BufferedStream(Stream* stm) :DecoratorStream(stm) {

    }
    //...
};

void Process() {

    //运行时装配
    FileStream* s1 = new FileStream();

    CryptoStream* s2 = new CryptoStream(s1);

    BufferedStream* s3 = new BufferedStream(s1);

    BufferedStream* s4 = new BufferedStream(s2);
}

类的规模：1+n+1+m