Re: Calling NSNumber class methods on NSDecimalNumber

FROM : Jens Alfke
DATE : Tue Apr 22 18:09:51 2008

On 22 Apr '08, at 8:19 AM, Dave Camp wrote:

> The problem is that I get the warning "initialization from distinct 
> Objective-C type" when I do this, because the NSNumber class methods 
> return a specific type instead of id.


It's safe; you'll just need to cast the return value to 
(NSDecimalNumber*) to avoid the warning.

I'm not sure I'd call this a bug in the headers. Most statically-typed 
OOP language have this kind of problem handling methods that are 
overridden to return a subclass instance. They could change the return 
type to "id", as other classes like NSDictionary do, but then you lose 
the type-checking. (There are several times I've accidentally assigned 
[NSMutableArray array] to an NSSet*, for example, and wasted time 
tracking down weird exceptions at runtime.)

—Jens