CODEWITHSUNDEEP
iphoneobjective-cnsmutablearraynull
stefanosn
stefanosn

Reputation: 3324

how to add nil to nsmutablearray?

NSArray *array = [[NSArray alloc] initWithObjects:@"ΕΛΤΑ",
                      @"ΕΛΤΑ COURIER", @"ACS", @"ACS ΕΞΩΤΕΡΙΚΟ", 
                      @"DHL", @"INTERATTICA", @"SPEEDEX", 
                      @"UPS", @"ΓΕΝΙΚΗ ΤΑΧΥΔΡΟΜΙΚΗ", @"ΜΕΤΑΦΟΡΙΚΕΣ ΕΞΩΤΕΡΙΚΟΥ", nil];

This is working because it has nil at the end.

But I add objects like this: addObject:name etc... So at the end I have to add nil I do this addObhect:nil but when I run the app it still crashes at cellForRowAtIndexPath:

how can I do this work?

Ok, I dont have to add nil

What is the reason that my app crashes then?

Upvotes: 54

Views: 49436

Answers (9)

mert
mert

Reputation: 1098

You need to add NSNull class and the best way to do it is like this:

NSArray *array = @[ @"string", @42, [NSNull null] ];

I personally recommend to use a specific value like 0 instead of null or nil in your design of your code, but sometimes you need to add null.

There is a good explanation from this Apple reference.

Upvotes: 8

Manjuhere
Manjuhere

Reputation: 151

pass your object through this method when adding to array to avoid attempt to insert nil object from objects crashes.

-(id) returnNullIfNil:(id) obj  {
    return (obj == nil) ? ([NSNull null]) : (obj);
}

[NSNull null] returns an null object which represents nil.

Upvotes: 2

Mike Weller
Mike Weller

Reputation: 45598

You don't need to call [addObject:nil]

The nil in initWithObjects: is only there to tell the method where the list ends, because of how C varargs work. When you add objects one-by-one with addObject: you don't need to add a nil.

Upvotes: 27

Adrian Kosmaczewski
Adrian Kosmaczewski

Reputation: 7956

If you must add a nil object to a collection, use the NSNull class:

The NSNull class defines a singleton object used to represent null values in collection objects (which don’t allow nil values).

Assuming "array" is of type NSMutableArray:

....
[array addObject:[NSNumber numberWithInt:2];
[array addObject:@"string"];
[array addObject:[NSNull null]];

Upvotes: 233

mr-sk
mr-sk

Reputation: 13407

You can't add nil when you're calling addObject.

Upvotes: 18

David Grant
David Grant

Reputation: 3477

If you really want a Null-ish item in your collection, NSNull is there for that.

Upvotes: 15

TechZen
TechZen

Reputation: 64428

You can't add an object to an NSArray because that class is immutable. You have to use NSMutableArray if you want to change the array after it is created.

Upvotes: 0

Tomen
Tomen

Reputation: 4854

nil is used to terminate the array

Upvotes: 6

mouviciel
mouviciel

Reputation: 67829

nil is not an object that you can add to an array: An array cannot contain nil. This is why addObject:nil crashes.

Upvotes: 5

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