>> how can the compiler know that '==' in this case is a NSString comparison?
> It can’t because it isn't. What’s being compared are raw pointers. The string 
> value is irrelevant.

Let me try to paraphrase, in order to check whether I am understanding 

Whenever I have two string literals @"XYZ" at different places in the same 
compilation unit,
and the XYZ are identical, then the compiler (or the Objective-C standard) make 
sure that
the pointers to those literals are identical?
In other words, the compiler unifies the two occurrences of the two literals, 
thus effectively storing only one literal?

> So, this technique is generally Not A Good Idea™.

If my understanding is correct, then I wholeheartedly agree.

That brings me to another question.  I've got this piece of code from an 
example on MLMediaLibrary.

This is how I start the whole thing:

  [mediaLibrary_ addObserver: self
                      forKeyPath: @"mediaSources"
                         options: 0
                         context: (__bridge void *) @"mediaLibraryLoaded"];

And this is the beginning of the corresponding KVO:

- (void) observeValueForKeyPath: (NSString *) keyPath   ofObject: (id) object
                       change: (NSDictionary *) change context: (void *) context
  MLMediaSource * mediaSource = [mediaLibrary_.mediaSources objectForKey: 
  if ( context == (__bridge void *) @"mediaLibraryLoaded" )

So what would be the proper way to do it?  Should I just define my own string 

Best regards, 


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