This is probably a naive question here but I'll ask it anyway.
I'm working with Core Audio (C API) on iOS and am mixing C with Objective-C. My class has the .mm extension and everything is working so far.
I've read in different places about Objective-C being slow (without much detail given - and I am not making any declaration that it is). I understand about not calling Objective-C from a Core Audio render callback, etc. and the reasons why.
On the other hand, I need to call in to the class that handles the Core Audio stuff from my GUI in order to make various adjustments at runtime. There would be some walking of arrays, mostly, shifting data around that is used by Core Audio. Would there be any benefit speed-wise from writing my functions in C and storing my variables in, say, vectors rather than NSMutableArrays?
I've only been working with Objective-C/iOS for a few months so I don't have any perspective on this.
Objective-C is slightly slower than straight C function calls because of the lookups involved in its dynamic nature. I'll edit this answer with more detail on how it works later if nobody else adds in the detail.
However, more importantly, you are optimizing prematurely. There's a VERY high chance that the extra overhead of Objective-C will have zero noticeable impact on your application's performance.
Take advantage of Objective-C's strengths to design the best written, most object-oriented application possible. If, and only if, testing shows performance problems, optimize those particular areas of the application.