Question

I am trying to scan through an NSMutableArray and remove all 0’s. (They are wrapped in NSNumber objects). I was trying to just use a for loop to search through, but I come across the issue that once I remove an object, it causes an index out of bounds issue for future iterations. I can’t think of a logical way to easily solve this issue.

My current code is this:

    for(int i =0; i < [array count]; i++)
{
    if(!abs([[array objectAtIndex: i] floatValue]) > 0.0)
    {
              [array removeObjectAtIndex: i];
    }
}

Is there a way to fix up my loop or use a special method/function to just eliminate all 0s?

Answer 1

I recommend using NSArray’s filteredArrayUsingPredicate: method with a simple block, like so:

NSPredicate *notZero = [NSPredicate predicateWithBlock:
    ^BOOL(id evalObject,NSDictionary * options) {
        return [evalObject boolValue];
    }];
array = [array filteredArrayUsingPredicate:notZero];

The logic in the block is simple, any float which is non-zero is truthy, and thus passes the predicate.