Cocoa provides the nice standard -[NSObject isEqual:] method for comparing equality of two objects, which is very convenient, but introducing nil values can throw a spanner in the works. Namely, doing -[someNilVariable isEqual:nil] will return nil as the message was sent to a nil object. This might well be what you intended, but I find myself often wanting the reverse; two nil objects should be considered equal.
So, here's a nice simple NSObject category to handle that:
@implementation NSObject (MAEqualityAdditions)
/* Like the standard -[NSObject isEqual:] method but can handle nil values.
*/
+ (BOOL)object:(NSObject *)object1 isEqual:(NSObject *)object2;
{
BOOL result;
if (object1 && object2)
{
result = [object1 isEqual:object2];
}
else
{
result = (object1 == object2);
}
return result;
}
@end
Update: As ever, Omni have beaten me to it. If you check out their frameworks, there's already a very nice bunch of macros that do the above, but also handle NSNull.