How to add a number of objects skipping nil objects to NSMutableArray?

Question

I need a method that would add a few objects (2-10) to my array, skipping these that are nils:

NSMutableArray *arr = [[NSMutableArray alloc] init];
[arr addObjectsSkipNils:obj1, obj2, obj3];

How I can write this method in an elegant way?

Each of the objects is either nil or a real object. I just don't want to write 3 statements, can it be done with 1? — Sergey Aldoukhov
– Sergey Aldoukhov, Commented Mar 29, 2013 at 19:52
Can't be done that way, even (especially) with non-nil values. The last value in the list must always be nil. — Hot Licks
– Hot Licks, Commented Mar 29, 2013 at 19:54
(Can be done with one long, tortuous statement using ?:, but I'd hardly advise it. Sometimes you actually have to write more than one statement. (Be thankful you're not doing it in assembler.)) — Hot Licks
– Hot Licks, Commented Mar 29, 2013 at 19:56
I could add the nil objects to dictionary, than filter out nils - but this is not nice... — Sergey Aldoukhov
– Sergey Aldoukhov, Commented Mar 29, 2013 at 19:56

Martin R · Accepted Answer · 2013-03-29 20:07:59Z

This category method would work:

@interface NSMutableArray (MyAdditions)
- (void)addObjectsSkipNilsWithCount:(NSUInteger)count objects:(id)obj, ...;
@end

@implementation NSMutableArray (MyAdditions)

- (void)addObjectsSkipNilsWithCount:(NSUInteger)count objects:(id)obj, ...
{
    va_list ap;
    va_start(ap, obj);
    // First object:
    if (obj != nil)
        [self addObject:obj];
    // Remaining objects:
    for (NSUInteger i = 1; i < count; i++) {
        id myobj = va_arg(ap, id);
        if (myobj != nil)
            [self addObject:myobj];
    }
    va_end(ap);
}
@end

Example:

NSMutableArray *a = [NSMutableArray array];
[a addObjectsSkipNilsWithCount:3 objects:@"foo", nil, @"bar"];
NSLog(@"%@", a);
// Output: ( foo, bar )

You have to specify the number of objects explicitly, because nil cannot be used as terminator for the variable argument list. (And bad things can happen if the count is greater than the actual number of objects supplied !)

Anoop Vaidya · Accepted Answer · 2013-03-29 19:54:12Z

0

You can use:

[yourMainArray removeObjectIdenticalTo:[NSNull null]];

Now if you want to copy this to arr you can do quite easily.

answered Mar 29, 2013 at 19:54

Anoop Vaidya

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2 Comments

Hot Licks Over a year ago

How did the nil values get into the array in the first place?

Sergey Aldoukhov Over a year ago

Yes, this is a chicken-and-egg problem.

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