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OK, here’s the deal:

I have 2 NSDocument subclasses, one for dealing with HTML documents, one for dealing with text documents. Both implement the same methods, with HTML being treated slightly differently (saving with a .html extension, for one thing). I have some code that looks like:

NSDocument *outputDocument;

if (YES == isHTML)
outputDocument = [[NSDocumentController sharedDocumentController] 
     openUntitledDocumentOfType: @"HTML Document" display:NO];
outputDocument = [[NSDocumentController sharedDocumentController] 
      openUntitledDocumentOfType: @"Text Document" display:NO];

[outputDocument doStuff];

Which gives warnings that ‘NSDocument may not respond to doStuff’. Not a big deal, I guess, since my subclass does respond to doStuff, but I’d like to fix it if I can. I tried variations on [([outputDocument class])outputDocument doStuff]; which didn’t work. Is there a way to cast a class at runtime?

Duh. NeverMind… Just typing outputDocument as id gets rid of the warnings… I should retake ObjC 101

I’ve never taken ObjC 101, but my natural (obsession with) tidiness leads me to ask, why not treat isHTML as a proper BOOL?

if (isHTML) { ... }
else { ... }

*It is a proper BOOL if it’s being declared as such… it’s just being explicitly tested for a YES value here - nothing wrong with it, just a matter of style. It’s probably actually better to do it the first way, since if isHTML was mistakenly declared as a pointer: *


it would generate a warning. Otherwise you’re just testing for nil, which is probably not what you intended. Also note the use of YES as the left value, to avoid = vs. == errors.

Another easy way to get rid of this warning is to declare -doStuff as an unimplemented category on NSDocument, similar to how an informal protocol is declared:

@interface NSDocument (DoStuffSupport)

This way you’ll suppress the warning but you won’t lose all such warnings in the process. – Bo