Including #includes in header file vs source file

Question

I like to put all my #includes in my header file then only include my header for that source file in my source file. What is the industry standard? Are there any draw backs to my method?

Answer 1

Generally, you only want to put the minimum necessary includes into a class header file, as anyone else who uses that header will be forced to #include all of them too. In larger projects, this leads towards slower builds, dependency issues, and all sorts of other nastiness.

Think of a header file as the public interface to your class. You don't want to saddle everyone who uses it with extra dependencies, unless they're necessary to be able to use the class.

Move anything that's only needed in the class implementation down into the source file. For other classes used in a header, only #include their headers if you actually need to know their size or contents in the header - anything else and a forward declaration is sufficient. Most cases, you only need to #include classes you're inheriting from, and classes whose objects are value members of your class.

This page has a good summary.