How to add nil to nsmutablearray?

Question

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

This works because in the end it has zero.

But I add such objects: addObject:name , etc .... Therefore, in the end I have to add nil, I do this addObhect: zero, but when I run the application, it still crashes with cellForRowAtIndexPath:

How can i do this?

Ok i don't need to add nil

What is the reason that my application will work?

Answer 1

You cannot add nil when you call addObject .

Answer 2

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

The NSNull class defines a singleton object used to represent null values ​​in collection objects (which do not allow nil values).

Assuming the "array" is of type NSMutableArray:

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

Answer 3

You do not need to call [addObject:nil]

nil in initWithObjects: only there to tell the method where the list ends, due to how C varargs works. When you add objects one by one using addObject: you do not need to add zero.

Answer 4

If you really need the Null-ish element in your collection, NSNull exists for this.

Answer 5

nil is used to complete the array

Answer 6

nil not an object that can be added to an array: an array cannot contain nil . This is why addObject:nil crashes.

Answer 7

You need to add NSNull , and the best way to do this is:

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

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

There is a good explanation for this Apple link .

Answer 8

You cannot add an object to an NSArray because this class is immutable. You must use NSMutableArray if you want to modify the array after creating it.

Answer 9

pass your object using this method when adding to an array to avoid trying to insert a nil object from objects .

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

[NSNull null] returns a null object that represents nil.