装饰模式
装饰模式
动态(组合)地给一个对象增加一些额外的职责。就增加功能而言,Decorator模式比生成子类(继承)更为灵活(消除重复代码&减少子类个数)。
class Stream
{
public:
virtual char* read(int size) = 0;
virtual void write(char* data,int size) = 0;
virtual void seek(int position) = 0;
}
class FileStream : public Stream
{
public:
virtual char* read(int size) override
{
//...
}
virtual void write(char* data,int size) override
{
//...
}
virtual void seek(int position) override
{
//...
}
}
class NetworkStream : public Stream
{
public:
virtual char* read(int size) override
{
//...
}
virtual void write(char* data,int size) override
{
//...
}
virtual void seek(int position) override
{
//...
}
}
class MemoryStream : public Stream
{
public:
virtual char* read(int size) override
{
//...
}
virtual void write(char* data,int size) override
{
//...
}
virtual void seek(int position) override
{
//...
}
}
class DecoratorStream : public Stream
{
public:
DecoratorStream(Stream* stream):stream_(stream){ }
virtual ~DecoratorStream(){ }
protected:
Stream* stream_;
}
class CryptoStreamDecorator : public Stream
{
public:
virtual char* read(int size) override
{
//...
stream_->read(size);
//...
}
virtual void write(char* data,int size) override
{
//...
stream_->write(data,size);
//...
}
virtual void seek(int position) override
{
//...
stream_->seek(position);
//...
}
}
class BufferStreamDecorator : public Stream
{
public:
virtual char* read(int size) override
{
//...
stream_->read(size);
//...
}
virtual void write(char* data,int size) override
{
//...
stream_->write(data,size);
//...
}
virtual void seek(int position) override
{
//...
stream_->seek(position);
//...
}
}
int main()
{
FileStream* fs=new FileStream();
CryptoStreamDecorator csd=new CryptoStreamDecorator(fs);
BufferStreamDecorator bsd=new BufferStreamDecorator(csd);
bsd->read(10);
bsd->seek(0);
bs->write("hello world!",13);
}