How to find object of certain kind in an NSArray?

Question

My first instinct is to

FooType *myFoo = nil;
for (id obj in myArray) {
    if ( [obj isKindOfClass:[FooType class]] ) myFoo = obj;
}

With all the goodies in Objective-C and NSArray, there's gotta be a better way, right?

Answer 1

Nope. That's how you would do it. Though there may be version that accepts a block in the new iOS4 API that might make it a little simpler.

Answer 2

With Blocks support (in iOS 4 or Snow Leopard):

FooType *myFoo = nil;
NSUInteger index = [myArray indexOfObjectPassingTest:^BOOL (id obj, NSUInteger idx, BOOL *stop) {
    return [obj isKindOfClass:[FooType class]];
}];
if (index != NSNotFound) myFoo = [myArray objectAtIndex:index];

It's not really any shorter. You might consider writing your own NSArray method to do so.

Answer 3

Like jtbandes mentioned, you can write an NSArray method as a category if you're going to be doing this a lot. Something like this:

@interface NSArray (FindClass)
- (NSMutableArray *) findObjectsOfClass:(Class)theClass
@end

then

@implementation NSArray (FindClass)
- (NSMutableArray *) findObjectsOfClass:(Class)theClass {
    NSMutableArray *results = [[NSMutableArray alloc] init];

    for (id obj in self) {
        if ([obj isKindOfClass:theClass])
            [results addObject:obj];
    }

    return [results autorelease];
}
@end

then when you want to use it just do:

NSMutableArray *objects = [myArray findObjectsOfClass:[FooType class]];

which should hold all of the objects of the specified class.

Disclaimer: not tested, sorry if something's wrong :/