int or NSInteger to NSUInteger for index

Question

I'm trying to (in Xcode5) use the 'removeObjectAtIndex' for an 'MutableArray' which takes an NSUInteger but the variable I'm using is an integer so I casted with (NSUInteger *) but I get a warning that says cast to 'NSUInteger *' (aka unsigned long *) from smaller integer type. I have not casted the variable 'second' in the code to keep the warning there but it is also an integer

-(void) moveObjectAtIndex:(NSUInteger *)oldIndex toNewIndex:(NSUInteger *)newIndex{
    id *member = [self.array objectAtIndex:*oldIndex];
    [self.array removeObjectAtIndex:*oldIndex];
    if ((NSInteger)newIndex >=(self.array.count)) {
        newIndex--; //i casted newIndex because I got a warning about ordered comparison of NSUInteger with NSInteger (I'm not sure if this is best solution)
    }
    [self.array insertObject:member atIndex: *newIndex];
}

-(void)moveObjectInArray:(NSMutableArray *)array{
    [array moveObjectAtIndex:(NSUInteger *) first toNewIndex:second];
}

Why the asterisks/pointers? Why not just pass these integers as parameters directly (and retrieve them directly)? You are less likely to confuse yourself, and you are not _doing_ anything with the pointers qua pointers (as far as I can see). — matt, Feb 21 '14 at 04:59
what you and @Chuck said regarding pointers and asterisk were totally on point. I made the suggestions everyone here said and that resolved the issues. Thanks — snapfish, Feb 21 '14 at 05:24

score 3 · Accepted Answer · answered Feb 21 '14 at 05:05

3

Your use of pointers is all wonky. id* should just be id and NSUInteger* should just be NSUInteger — you don't want a pointer to a pointer to an object or a pointer to an integer here.

answered Feb 21 '14 at 05:05

Chuck

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score 2 · Answer 2 · answered Feb 21 '14 at 05:12

What's problem for you of using just NSUInteger rather than NSUInteger* ?

-(void) moveObjectAtIndex:(NSUInteger)oldIndex toNewIndex:(NSUInteger)newIndex{
    id member = [self.array objectAtIndex:oldIndex]; //Here is id, id* is wrong
    [self.array removeObjectAtIndex:oldIndex];
    newIndex = newIndex >= self.array.count ? : self.array.count - 1; // Here should be self.array.count - 1, not newIndex-1
    newIndex = MIN(_cloudListArray.count, newIndex);
    [self.array insertObject:member atIndex:newIndex];
}

score -1 · Answer 3 · answered Feb 21 '14 at 04:58

In the following statement

if ((NSInteger)newIndex >=(self.array.count))

you are typecasting pointer to NSInteger. It should be

if ((NSInteger)*newIndex >=(self.array.count))

Still, you should be careful with typecasting and be wary of their consequences due to any signed/unsigned conversion or data loss.

Also, in this line

[array moveObjectAtIndex:(NSUInteger *) first toNewIndex:second];

type of first should be NSUInteger * or of same size. Please note that long is 64-bit in 64-bit environment and typecasting as smaller pointer type to larger pointer type will yield undefined behaviour. Same applies to second. One solution is that use temporary variable and then copy back the result.

can you give me an example of how to use a temporary variable? if i make NSUInteger *random = first the same warning applies and I cant use a variable of type id. — snapfish, Feb 21 '14 at 05:08

int or NSInteger to NSUInteger for index

3 Answers3