NSNumber query

[MikeF]

Hello
below i've initialized 2 number objects using both allowable methods(as referenced on p 326). Am i right in saying that myInt1 and myInt2  cannot be changed to contain new values after their initialization?

NSNumber *myInt1 = [NSNumber numberWithInt: 100];  

NSNumber *myInt2;
myInt2 = [[NSNumber alloc] initWithInt:200];
   

[TotalLuck]

NSNumber is just a typeDef  for an int .  so there is no need to [NSNumber alloc]..


your first  statement is correct

Code: (Objective-C)

NSNumber *myInt1 = [NSNumber numberWithInt: 100];  

after you declare myInt1 in that statement you can reassign it at any time using the same statement as such

Code: (Objective-C)

myInt1 = [NSNumber numberWithInt: 99];  

so not this

Code: (Objective-C)

[color=red][font=Verdana]NSNumber *myInt2;
myInt2 = [[NSNumber alloc] initWithInt:200][/font][/color];

this

Code: (Objective-C)

NSNumber *myInt2= [NSNumber initWithInt:200];

hope that helps..

[MikeF]

Hello,
how can i change the contents of an NSNumber object easily? Is there a setter for this? I've noticed that when i step through my code with the debugger  it seems to happily accept the following lines of code, although it's obviously the wrong thing to do.

All i want to do is change the value from 100 to 200?


NSNumber *myInt1 = [NSNumber numberWithInt: 100];
NSNumber *myInt1 = [NSNumber numberWithInt: 200];



I'm new to the language so please excuse my lack of knowledge.. , but on the face of it i guess I'm struggling to understand the point of NSNumbers as apposed to say 'int' ?.  I realize you can store them arrays, and I'm guessing this fact is crucial for reasons i don't understand yet.

[Jake]

Do recall ( from chapter 8 ) that you, as the programmer, are not responsible for releasing objects from class that you did not created. NSNumber is.  What you done is slightly wrong (however, it's almost right) as you wrote this:

Code: (Objective-C)

// The wrong way
NSNumber *myInt1 = [NSNumber numberWithInt: 100];
NSNumber *myInt1 = [NSNumber numberWithInt: 200]; 

Once you declare an pointer to an object, you do not need to re-declare it again unless it is already destroy. (Actually, I think that if you re-declare it, it cause problems; I'm not sure on this though.)

The more correct way is this:

Code: (Objective-C)

// The correct way 
NSNumber *myInt1 = [NSNumber numberWithInt: 100];
myInt1 = [NSNumber numberWithInt: 200]; 

As you can see, I declare a pointer call myInt1 pointing to a NSNumber with the integer100. Reassigning a value to myInt1 is fine.

Steve (or some other expert), please tell me if my answer is right or not (as I'm not completely faithful if I answer  correctly)!