checking if an array doesn't contain a certain object

Question

is there a class available to check if an array doesn't contain an object? I want to do something like

if [(myarray doesntContain @"object")]

is this possible

@Alx, when you're choosing the tags for your question, it's generally a good idea to make sure one of them is the language you're asking the question for =) — Rob, Aug 21 '10 at 10:15
In which case, which sort of array? A basic C array, or a NSArray? — Stephen, Aug 21 '10 at 10:18
Remember to add those details to the question when asking, most of us can't read minds. — Georg Fritzsche, Aug 21 '10 at 10:34

score 104 · Accepted Answer · answered Aug 21 '10 at 10:29

104

For NSArray use -containsObject::

if (![myarray containsObject:someObject]) {
    // ...
}

answered Aug 21 '10 at 10:29

Georg Fritzsche

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i know about contains object i want to see if there isnt a specific object in the array and if there isnt to add one. i know how to add i just dont know how to check if an object is missing.. – Alex Stelea Aug 21 '10 at 10:31
1

@Alx: Thats why the `!` is there, its basically *"if not (array containsObject)"*. There isn't a specific `-doesntContainObject:` as its trivial to use `!` or `== NO`. – Georg Fritzsche Aug 21 '10 at 10:33
1

however one small error i have if (![self.favoritesArray containsObject:@"added"]) { [self.favoritesArray addObject:@"added"]; } else if ([self.favoritesArray containsObject:@"added"]) { [self.favoritesArray removeObject:@"added"]; } this is my code and when i press the button it doesn remove the added option... – Alex Stelea Aug 21 '10 at 10:56
@Alx: You can't add or remove objects with a `NSArray`, use `NSMutableArray`. If you still have problems then, you should open a new question and add some more details. Also note that `if (!...) { ... } else { ... }` is sufficient (you don't have to test twice) and that maybe `NSMutableSet` would be a better fit for you. – Georg Fritzsche Aug 21 '10 at 11:09
i know and my array is a mutable one. – Alex Stelea Aug 21 '10 at 11:18
By the way: if your array consists of custom objects you created, you need to implement `-(BOOL)isEqual:(id)anotherObject;` method on them in order to `-containsObject:` work properly – Glogo Sep 03 '14 at 13:26

Alex Gray · Answer 2 · 2012-04-27T16:09:04.850

I wrote an NSArray category to achieve these negated checks via instance methods, as you had originally requested.. The first is for an array-type set group of objects, the latter for a singular check. These return YES in the case that the array instance DOES NOT contain the passed object or objects. Why? Exclamation marks confuse me.

NSArray+Additions.h

-(BOOL)doesNotContainObjects:(id<NSFastEnumeration>)enumerable;

-(BOOL)doesNotContainObject:(id)object;

NSArray+Additions.m

-(BOOL)doesNotContainObjects:(id<NSFastEnumeration>)enumerable {
   for (id x in enumerable) {
     if ([self containsObject:x]) return NO; // exists, abort!
   }
   return YES;   // it ain't in there, return TRUE;
}
- (BOOL)doesNotContainObject:(id)object {
  if ([self containsObject:object]) return NO; return YES;
}

score 0 · Answer 3 · edited May 23 '17 at 11:54

0

If you're dealing with an NSArray, your first port of call should probably be the Apple documentation for NSArray, and probably the method containsObject, there's an example in this question.

edited May 23 '17 at 11:54

Community

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answered Aug 21 '10 at 10:22

Rob

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i know about contains object i want to see if there isnt a specific object in the array and if there isnt to add one. i know how to add i just dont know how to check if an object is missing.. – Alex Stelea Aug 21 '10 at 10:31
So invert the call to `containsObject` as Georg has indicated in his answer =) – Rob Aug 21 '10 at 10:42

checking if an array doesn't contain a certain object

3 Answers3