Question

I have a category of NSMutableArray which has a deletion method:

@interface NSMutableArray(MyCategory)
- (void) deleteItemsMatchingCriteria: (SomeCriteria) theCriteria;
@end

How should this be implemented?

To iterate through arrays I usually use enumerateObjectsUsingBlock: but of course one cannot delete an item from the array while in the middle of the iteration.

Is there a canonical way of doing this for arrays in general, and does it differ if the method doing the deletion is a category of the array?

Answer 1

The simplest way to do it would be to use indexesOfObjectsPassingTest: method:

[self removeObjectsAtIndexes:[self indexesOfObjectsPassingTest:
    ^BOOL (id element, NSUInteger i, BOOL *stop) {
        return /* YES if the object needs to be removed */;
    }]
];