Should I put many functions into one file? Or, more or less, one function per file?

Question

I love to organize my code, so ideally I want one class per file or, when I have non-member functions, one function per file.

The reasons are:

1. When

Answer 1

An old programming professor of mine suggested breaking up modules every several hundred lines of code for maintainability. I don't develop in C++ anymore, but in C# I restrict myself to one class per file, and size of the file doesn't matter as long as there's nothing unrelated to my object. You can make use of #pragma regions to gracefully reduce editor space, not sure if the C++ compiler has them, but if it does then definitely make use of them.

If I were still programming in C++ I would group functions by usage using multiple functions per file. So I may have a file called 'Service.cpp' with a few functions that define that "service". Having one function per file will in turn cause regret to find its way back into your project somehow, someway.

Having several thousand lines of code per file isn't necessary some of the time though. Functions themselves should never be much more than a few hundred lines of code at most. Always remember that a function should only do one thing and be kept minimal. If a function does more than one thing, it should be refactored into helper methods.

It never hurts to have multiple source files that define a single entity either. Ie: 'ServiceConnection.cpp' 'ServiceSettings.cpp', and so on so forth.

Sometimes if I make a single object, and it owns other objects I will combine multiple classes into a single file. For example a button control that contains 'ButtonLink' objects, I might combine that into the Button class. Sometimes I don't, but that's a "preference of the moment" decision.

Do what works best for you. Experiment a little with different styles on smaller projects can help. Hope this helps you out a bit.