Object Oriented pattern in C ?

Question

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Can you write object oriented code in C?

I am writing a large application in C and have heard that prior to the advent of C++ programmers used to implement the "Object Oriented" pattern in C. My question is what is the usual form this pattern takes? and how would I go about implementing such an OOP pattern in a modern C application?

Answer 1

I used to simply adopt naming conventions for a structure and associated "methods". Each method would begin with e.g. CANDIDATE_ for a candidate object, and be associated with a typedef CANDIDATE { ... }, and be in a file Candidate.c

Answer 2

Where a C++ object has methods, object-style 'C' takes a struct full of function pointers. The functions corresponding to a member function have an explicit data argument that takes the place of the implied 'this' pointer.

Subclasses use function-pointer structs of the same type, with different function pointers to indicate overridded methods.

Answer 3

Here are a few helpful links to guides on Object Oriented C:

• Object Oriented Programming with C - A very thorough treatment of the subject.
• Phil's guide to object-oriented C - This is a rather simplistic approach to the subject, imo.
• GObject Reference Manual - GObject is used heavily throughout Gnome and GTK+ applications (mostly on Linux) and therefore provides a thorough example of Object Oriented C in the real world.

Answer 4

An additional link from someone who wrote several OO frameworks for C.