In this quick postscript we’ll look into a simple way to clean up our various SDL resources with variadic templates
and template specialization. This will let us clean up all our resources with a single simple call:
cleanup(texA, texB, renderer, window) instead of calling all the corresponding
saving ourselves a lot of typing.
We’ll do this by creating a variadic function
cleanup that will take the list of SDL resources to be free’d and then
define specializations of it for each resource we’ll be passing, eg. for
and so on.
If you’re unfamiliar with the C++11’s varidic templates and rvalue references and forwarding features it may be useful to do some reading to get some background before continuing on to the implementation. The implementation of our cleanup function however is actually quite simple. We have a single variadic template function that calls one of our specialized cleanup functions and then recurses to iterate through the list of arguments. Since the code for this functionality is so short I’ve left the detailed explanations in the comments, so be sure to read through them.
To see the usefulness of this cleanup utility let’s see how it compresses our calls to the various
SDL_Destroy/Free* functions throughout Lesson 1.
In lesson 1 if we found that our bitmap or texture wasn’t created successfully we’d need to destroy
the renderer and window before quitting out of SDL and exiting with a failure code. With
we can compress these two lines down to a single call.
We can also compress the three lines used to free all the resources (texture, renderer and window) at the end of
Lesson 1 down into a single
cleanup call, passing all the resources we want to free.
cleanup can also be used as a drop-in replacement for the various
SDL_Destroy/Free* functions, although this
doesn’t really give us much benefit as far as compressing lines goes.
That’s all for this postscript, try out
cleanup yourself by converting your code from Lesson 1 to use it instead of
calling all the
SDL_Destroy/Free* functions manually. If you run into any issues or have any questions
please post a comment below.
I’ll see you again soon in Lesson 2: Don’t Put Everything in Main!