I'm interested in discussing string literals in Objective-C and would like to know 1. if there's a preferred paradigm / style and 2. what (if any) the performance implications might be.
There are parts of the Cocoa / CocoaTouch frameworks that use strings as identifiers. Some examples in Cocoa / CocoaTouch...
-[NSNotificationCenter addObserver:selector:name:object:] -[UITableView dequeueReusableCellWithIdentifier:] -[UIViewController performSegueWithIdentifier:sender:]
I find myself most often declaring a global variable within the class like so...
NSString * const kMySegueIdentifier = @"Awesome Segueueueueue";
For segue identifiers, I will often times expose the variable in the header file
extern NSString * const kMySegueIdentifier; so that other modules can reuse it.
The same behaviors can be accomplished with preprocessor macros:
#define kMySegueIdentifier @"Awesome Segueueueueue". I believe this would also prevent the app from consuming memory to hold these globals. I cringe a little at this syntax however because it exposes the "implementation details" of my string literal constants.
Both of these lines accomplish an end goal of abstracting the string into being easy to remember, type correctly, and will generate compile warnings / errors, is one actually better then the other? What are the situations that would arise where one would be preferred over the other?