Where is pimpl used in C++ apps/libs? any examples?

Question

pimpl idiom allows to reduce compilation dependencies in projects and have binary compatibility at the same time.

In other words you can change private implementation of a class without the need to recompile client's code.

Where can I find examples of such approach? Do you know any open source libraries or apps that uses it?

I know about QT and Poco:

D-Pointer - Qt Wiki
poco/IPAddress.h at develop · pocoproject/poco (but is this correct to include 'impl' header file in the 'public' header file? Any change in that private impl will cause recompilation).

I've just found an older, similar question: https://stackoverflow.com/questions/8972588/is-the-pimpl-idiom-really-used-in-practice — fen, Jan 05 '18 at 09:10

Alexander V · Answer 1 · 2018-01-04T20:58:16.007

2

Where can I find examples of such approach? Do you know any open source libraries or apps that uses it?

Qt. Specific module example: QGraphicsItem.cpp, filled with d_ptr. Private part interface. The whole thing with both public and private modules.

A private implementation makes a lot of sense in case of porting the whole library/framework to a different platform. You just put a different files for implementation in while keeping the public interface as is. And the implementation is accessible via d_ptr->.

For the curious: non-Qt Pimpl C++ 11 example.

edited Jan 04 '18 at 20:58

answered Jan 04 '18 at 20:19

Alexander V

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yes, yes, QT heavily uses this pattern. Do you know other libraries? – fen Jan 04 '18 at 20:55

Where is pimpl used in C++ apps/libs? any examples?

1 Answers1