I wrote a header file with my class that contains static members, Do I have to create a separate file for this class to initilialize these static members? or can i just instantiate them outside the class definition in the header file and will that be good or bad practice?
Defining statics (which is what you are incorrectly referring to as "instantiation" or "initialization") in a header file is bad practice more often than not.
If the header file is #include'd by more than one source file, then the definition of that static member usually needs to be in a separate source file. Otherwise, the one-definition rule is violated. Practically that usually results in a linker error, without creating an executable.
There are some tricks that allow you to get away with placing the definition of a class static in a header file, but they usually involve coercing the compiler to create a definition in only one object file. Compilers don't do that by default.
If the header file is only #include'd by one source file, it makes no difference. However, the purpose of placing declarations in a header file is usually to allow those declarations to be used by more than one distinct source file.
Last edited by grumpy; 03-04-2013 at 02:03 PM.
Originally Posted by grumpy
How would you go about initializing the class members in a separate implementation file and then including that in the main source file? So for example I have my class declarations in the header file then in my implementation file I include that header file and initialize the members of that class using the :: operator, How would I go about linking those two together in my main source file? would I have to include my cpp file after I include the header file?
Compile all .cpp files separately, then link them. How to do that depends on your compiler/IDE.
Typically, the process is as follows:
- To do it in an IDE, just add all .cpp files to your project and build it.
- With a compiler, you specify all .cpp files for compiling with appropriate flags, for example: g++ a.cpp b.cpp -o out.exe (don't recall the exact flags for g++, be warned...)
Never include .cpp files.
that command will work just fine.
if you want the compiler to be a bit more verbose about what you're doing wrong (nobody writes perfect code - not even elysia) you can add -Wall and -Wextra, or even -pedantic. you can even add -Werror if you want warnings to be treated as errors. if you want an easier time debugging with gdb, add the -g option. this is, of course, assuming you're using G++. if you're using a different compiler, you'll need to research the options, as I am most familiar with G++, and my knowledge is pretty weak on all the others.
