Question

I have found many discussions about NSMutableArray vs NSArray.
It’s very interesting and i understand that you cannot add or delete objects inside a NSArray

But is it possible to change objects in a NSArray ?

I mean, if i have a NSArray of NSNumber, can i change the NSNumber in the NSArray or should i use a NSMutableArray to be able to modify values of objects in the NSArray ?

Answer 1

NSArray does not let you exchange the elements (nor append or remove them). If you had an NSArray of mutable objects, say NSMutableStrings you could modify the objects without changing the array.

Since Cocoa does not contain a mutable variant of NSNumber you cannot do that with number objects, though.

Example:

// immutable array, immutable elements: no way to change anything.
NSArray *array1 = @[@1, @2, @3];

// immutable array of mutable elements:
NSArray *array2 = @[[@"1" mutableCopy], [@"2" mutableCopy], [@"3" mutableCopy]];
NSLog(@"Step 1: %@", array2); // prints "1, 2, 3"

// now we change one of the elements of the immutable array:
[array2[0] appendString:@".1"];
NSLog(@"Step 2: %@", array2); // prints "1.1, 2, 3"

Long story short:

Can i modify data inside an NSArray?

Yes.