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Documentation at the AppleDeveloperConnection:

See FoundationCollections for an overview; see DesignArray for a critique of the array design in general

NSArray implements -(BOOL)doesContain:(id)anObject which returns true if the array contains anObject, by identity.

Note that the same behavior can be gotten through documented methods with the following code:

And in fact I imagine this is how -doesContain: is implemented.

Another excellent method that NSArray provides is -(void) makeObjectsPerformSelector:(SEL)aSel

[myArray makeObjectsPerformSelector:@selector(stroke)];

Yeah, but if they were thinking clearly, they would have returned a new array containing the results of each method call.

Like this? - (NSArray *)makeObjectsPerformSelectorAndReturnResults:(SEL)selector { NSMutableArray *results = [NSMutableArray array]; NSEnumerator *e = [self objectEnumerator]; id obj; while (obj = [e nextObject]) { if ([obj respondsToSelector:selector]) [results addObject:[obj performSelector:selector]]; } return results; }

Yeah, thanks! I didn’t expect code…this could be useful.

There are several methods of this sort in cocoadev’s NSArrayCategory.

I don’t know if the code above should be considered reliable; there are lots of selectors where the methods don’t return objects. Although I don’t think there’s any two method signatures with differing return types, there could be in the future. I’ve been working on a catch-all for this in another context. It’s not done yet, but when it is I’ll see about posting it.

Note that Cocoa already provides a similar method, via valueForKey:. These two lines are basically equivalent:

newArray = [array makeObjectsPerformSelectorAndReturnResults: @selector( someMethod )]; newArray = [array valueForKey: @”someMethod”];

As a bonus, the built-in method will autobox return values from methods that return primitives and it will also grab ivars directly if you provide its name and there’s no accessor method.

Check out the -mapUsingSelector: method of the NSArray+Functional category:

It allows you to do the same but with variable arguments selectors.

NSArray *a = [NSArray arrayWithObjects:@”a”, @”ab”, @”abc”, @”bc”, @”c”, nil];

NSArray *x = [a filterUsingSelector:@selector(hasPrefix:), @”a”, nil]; NSArray *y = [a mapUsingSelector:@selector(uppercaseString), nil]; NSArray *z = [a reduceUsingSelector:@selector(stringByAppendingString:)];


x: (a, ab, abc) y: (A, AB, ABC, BC, C) z: aababcbcc

Sample Code:

*IteratingThroughAnArray *SortUsingSelector *TerminateExplicitListWithNil