Monday, August 2, 2010
Assignment: Case Study 8
We have an inhouse C++ SDK that exposes fixed interface to read and write JPEG, TIFF & PDF files. There is a sniffer class that tells us which type of file type it is and based on that we create the instance of FileFormat (JPPEG, TIFF, PDF) class using a factory. The problem is that for PNG we have taken open source implementation and it doesn’t conform to our existing C++ interface. Please suggest what you believe is the best approach.
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Is it possible to add PNG file type also to the existing factory since we already have the implementation for the same? Pls don't ask me the code, i don't know... :)
ReplyDeleteWe can have a PNG class derived from the base class as in other cases and wrap the PNG library functionality with in this class i.e. having PNG library object/pointer as an member varaiable of this class and use this object to do the actual tasks basically providing a adapter class as per new hierarchy of ours and underlying delegate the tasks to PNG library object/pointer.
ReplyDeleteWrap an existing class with a new interface.
ReplyDeleteAdapter design pattern.
Add PNG class to existing factory.
ReplyDeleteSo now based on type we can get PNG obj,
Call Read & Write of PNG class( as SDK is not supporting for PNG type)
This is a case of Adapter.
ReplyDeleteclass IInterface
{
ReadImage() = 0;
WriteImage() = 0;
}
class PNGInterface : IInterface
{
private:
PNGAdaptor *m_pPNGAdaptor;
public:
ReadImage()
{
m_pPNGAdaptor->ReadImage();
}
WriteImage()
{
m_pPNGAdaptor->WriteImage();
}
};
class PNGAdapter
{
private:
PNGImpl *m_pImpl;
public:
ReadImage()
{
m_pImpl->ReadPNG();
}
WriteImage()
{
m_pImpl->WritePNG();
}
}