On Nov 3, 2008, at 11:30 AM, Gordon Apple wrote:
Is "self" even defined for a class object?
Yes.
If so, should case 1 (or
similar) be the assumed implementation for all of Cocoa? If not,
then,
IMHO, the docs in general should specify which is is for each factory
method.
Either way, the docs could be clearer, hence Jim's suggestion to file
a Radar.
--Andy
On 11/3/08 10:06 AM, "[EMAIL PROTECTED]"
<[EMAIL PROTECTED]> wrote:
On Nov 3, 2008, at 10:53 AM, Gordon Apple wrote:
The following example is one of several I have run into recently.
Inheritance is as follows: CAKeyframeAnimation:
CAPropertyAnimation :
CAAnimation. CAKeyframeAnimation has no explicit initializer or
factory
method. Dudney's book uses [CAKeyframeAnimation animation] to
create an
object. However, CAKeyframeAnimation has no such factory method.
CAAnimation does. Why should I assume that the "animation" factory
method
will return an object of class CAKeyframeAnimation instead of
CAAnimation
when it is not re-defined in CAKeyframeAnimation.h?
The docs say that CAKeyframeAnimation shoud be created with the
inherited (from CAPropertyAnimation) animationWithKeyPath factory
method.
That raises the same issue.
Is there a basic assumption that such factory methods are
implicitly
redefined for all subclasses?
In Objective-C, classes are objects with inheritance. What you'll get
back from a class convenience method is going to depend on how its
implemented (and not necessarily whether it is redefined by a
subclass.)
Consider
@interface Person : NSObject
+ (id)person
@end
@interface Child : Base
@end
Case #1
@implementation Person
+ (id)person
{
return [[[self alloc] init] autorelease];
}
@end
Case #2
@implementation Person
+ (id)person
{
return [[[Person alloc] init] autorelease];
}
@end
In case #1, [Child person] will return a Child instance to us.
In case #2, [Child person] will return a Person instance to us.
I think the CoreAnimation authors intended for case #1, but that's
not
what the documentation says.
Creates and returns a new CAAnimation instance.
+ (id)animation
Return Value
An CAAnimation object whose input values are initialized.
I'd recommend filing a bug against the documentation for
clarification/
correction.
Jim
G. Apple
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