iOS5 Core Data and NSNumber is there autoboxing/unboxing? - ios

Question

Coming from Java, I'm pretty used to autoboxing, where an int is automatically wrapped to an Integer when needed, and an Integer may be unboxed into a primitive. Is there something similar that I can rely upon in iOS5?
currently, I'm using core data, and it takes a lot of typing to keep having to type
number.intValue
//or
number.boolValue
is there some way to use an NSNumber directly in equations and such? for example:
int x = 5+ nsNumberInstance;
Furthermore, every time I need to re-assign a number in the core data, I'm creating a new object like this.
managedObject.dynamicProperty = [NSNumber numberWithInt: int];
is there a better way to change the value of an already created NSNumber? What kinds of nifty shortcuts may I use to save myself from carpal tunnel 10 years from now?
Thank you!

Answer 1

Actually, when you are in your data model, and you use the "Create NSManagedObject subclass" menu item, there is an option that you can select titled "Use scalar properties for primitive data types".
This automatically handles this for you in many cases.
Here are some examples:
BOOL:
#property (nonatomic, retain) NSNumber * aBool;
becomes
#property (nonatomic) BOOL aBool;
NSDate:
#property (nonatomic, retain) NSDate * aDate;
becomes
#property (nonatomic) NSTimeInterval aDate;
Integer 32:
#property (nonatomic, retain) NSNumber * aNumber;
becomes
#property (nonatomic) int32_t aNumber;
and
Float:
#property (nonatomic, retain) NSNumber * aFloat;
becomes
#property (nonatomic) float aFloat;
NSDecimalNumber and NSString stay the same.
You can change these yourself in the previously generated header file if you have already generated the subclasses and the accessor methods will automatically update without having to re-generate the subclass.

Answer 2

Outside of Cocoa bindings, I can't think of many other places that have autoboxing of scalar types in Cocoa or Cocoa touch, so unfortunately you're out of luck there.
You don't really gain anything by working with NSNumbers in calculations, so dealing with the objects there isn't really necessary. It's much easier to work with scalar types, and then convert back and forth between NSNumbers when storing these numbers in Core Data, arrays, etc. The one case where you'd want to stay in this form would be NSDecimalNumbers, which do not represent numbers as your standard floating point values, and thus avoid the glitches you see when trying to work with decimals in those types.
Core Data stores objects, so you're not going to get around that at a base level, but you can make your life a little easier by using custom accessors on your NSManagedObject subclasses that take and return scalar values. Apple has an example of this in the "Managed Object Accessor Methods" section of the Core Data Programming Guide, where they show how to set up an accessor for a CGFloat value, instead of using an NSNumber:
#interface Circle : NSManagedObject
{
CGFloat radius;
}
#property CGFloat radius;
#end
#implementation Circle
- (CGFloat)radius
{
[self willAccessValueForKey:#"radius"];
float f = radius;
[self didAccessValueForKey:#"radius"];
return f;
}
- (void)setRadius:(CGFloat)newRadius
{
[self willChangeValueForKey:#"radius"];
radius = newRadius;
[self didChangeValueForKey:#"radius"];
}
#end
As a side note, using the dot syntax for -intValue and -boolValue, while it works, is not recommended. These are not properties, but one-way methods that extract values from the NSNumbers. Use brackets when dealing with them to make this clear in your code.