isKClass: I think tests to see if you are a subclass of a given
class. Its what I have used before.
This is even a bit restricting since it may not tell you all you need
to know to be compatible. For instance, it may be that the object
subclasses NS but still implements the protocol you need - so
you can call conformsToProtocol: to see if this is true. If there is
a formal protocol defined, this is probably the best way to check if
the object is what you expect.
May 7, 2006, at 8:41 AM, Ben Dougall wrote:
hello,
regarding finding out if an object instance is a particular type of
class or not
which should be used out of the following three?:
if( [ isMClass:[AClass class]] ) {
if( [ class] == [AClass self] ) {
if( [[ className] isEqualToString:@"AClass"] ) {
i suppose the last one is only necessary if you're dealing with
class names in strings, otherwise not necessary. i'm currently
using [ class] == [AClass self] but am wondering if it's K?
thanks, ben
Do not post admin requests to the list. They will be ignored.
Cocoa-dev mailing list (Cocoa-dev (AT) lists (DOT) apple.com)
Help/Unsubscribe/Update your Subscription:
%40mac.com
This email sent to tblanchard (AT) mac (DOT) com
Do not post admin requests to the list. They will be ignored.
Cocoa-dev mailing list (Cocoa-dev (AT) lists (DOT) apple.com)
Help/Unsubscribe/Update your Subscription:
%40developershed.com
This email sent to bsdarchive (AT) developershed (DOT) com

hello,

regarding finding out if an object instance is a particular type of
class or not

which should be used out of the following three?:

if( [ isMClass:[AClass class]] ) {

if( [ class] == [AClass self] ) {

if( [[ className] isEqualToString:@"AClass"] ) {

i suppose the last one is only necessary if you're dealing with class
names in strings, otherwise not necessary. i'm currently using
[ class] == [AClass self] but am wondering if it's K?

thanks, ben

Do not post admin requests to the list. They will be ignored.
Cocoa-dev mailing list (Cocoa-dev (AT) lists (DOT) apple.com)
Help/Unsubscribe/Update your Subscription:
%40developershed.com

This email sent to bsdarchive (AT) developershed (DOT) com

5/7/06, Ben Dougall <bend (AT) freenet (DOT) co.ukwrote:

regarding finding out if an object instance is a particular type of
class or not

The basic answer is to use -isKClass:, like this:

if ([ isKClass:[NSString class]]) {
// Do something stringy with
}

However, if you just need to know whether you can call some method on
the object, you can be more general and do this:

if ([
respondsToSelector:@selector()]) {
// Call myMethod: on the
}

Larry

Do not post admin requests to the list. They will be ignored.
Cocoa-dev mailing list (Cocoa-dev (AT) lists (DOT) apple.com)
Help/Unsubscribe/Update your Subscription:
%40developershed.com

This email sent to bsdarchive (AT) developershed (DOT) com

5/7/06, Ben Dougall <bend (AT) freenet (DOT) co.ukwrote:
Todd, thanks for the reply.

Sunday, May 7, 2006, at 05:03 pm, Todd Blanchard wrote:

isKClass: I think tests to see if you are a subclass of a given
class. Its what I have used before.

i'm not after subclasses though -- just is of a particular type or not.
so [ class] == [AClass self] works fine but is there any reason
i should use isMClass instead of that? (isMClass is the
one that's appropriate for me out of isMClass and isKClass).
-isKClass: actually returns YES if the object is a member of the
given class or is a subclass of the given class. This is probably the
behavior you want, because say you're testing an object that's passed
into the method: If the user of the method passes an NSMutableString
but your class only checks for isMClass:[NSString class], then
your method won't work. So I would go with -isKClass:.

Larry

Do not post admin requests to the list. They will be ignored.
Cocoa-dev mailing list (Cocoa-dev (AT) lists (DOT) apple.com)
Help/Unsubscribe/Update your Subscription:
%40developershed.com

This email sent to bsdarchive (AT) developershed (DOT) com

Am 07.05.2006 um 17:41 schrieb Ben Dougall:
regarding finding out if an object instance is a particular type of
class or not

Just to play the party pooper here: Keep in mind that, *in general*
it's a sign of a mistake in your design if you need to check for a
particular class. Especially in Cocoa, it is perfectly fine that an
object may not be of a particular class, but rather of a class that
implements the same methods or a subclass of a particular class. Even
more importantly: NSString and several other fundamental classes of
Foundation are actually class clusters and the class itself is an
abstract base class. So, e.g. checking whether an object is of class
NSString will always return false, because you only get objects of
NSMutableString, NSCFString or whatever

So, if you can, use conformsToProtocol, respondsToSelector or
similar methods to check for the actual feature you need, and not for
a particular class name.

Cheers,
-- M. Uli Kusterer
http://www.zathras.de

Do not post admin requests to the list. They will be ignored.
Cocoa-dev mailing list (Cocoa-dev (AT) lists (DOT) apple.com)
Help/Unsubscribe/Update your Subscription:
%40developershed.com

This email sent to bsdarchive (AT) developershed (DOT) com

May 7, 2006, at 11:22 AM, Uli Kusterer wrote:

Am 07.05.2006 um 17:41 schrieb Ben Dougall:
>regarding finding out if an object instance is a particular type
>of class or not
>
Just to play the party pooper here: Keep in mind that, *in
general* it's a sign of a mistake in your design if you need to
check for a particular class. Especially in Cocoa, it is perfectly
fine that an object may not be of a particular class, but rather of
a class that implements the same methods or a subclass of a
particular class. Even more importantly: NSString and several other
fundamental classes of Foundation are actually class clusters and
the class itself is an abstract base class. So, e.g. checking
whether an object is of class NSString will always return false,
because you only get objects of NSMutableString, NSCFString or
whatever

So, if you can, use conformsToProtocol, respondsToSelector or
similar methods to check for the actual feature you need, and not
for a particular class name.

Another gotcha to look out for in specific class checking is if the
class ends up being used by Cocoa Bindings at all, the bindings
observing goo will end up making a subclass of your class which is
what all your actual objects will end up being. I.e. all your MyClass
objects actually end up becoming KVMyClass objects instead.
Similarly, fault objects or forwarding proxy objects may implement -
isMClass: or -isKClass: to pass along the call to the
'real' object involved since they are acting as if they are some
other class.

Comparing specific class pointers or class names will break in all of
these sorts of situations where other code is playing tricks with the
runtime. Since things like key-value-observing are most definitely
not local to your own code, and you can't guarantee that Apple won't
change implementations of Cocoa features to play more of these sorts
of tricks in the future, be VERY careful about specific class checks.

Hope this helps,
- Greg

Do not post admin requests to the list. They will be ignored.
Cocoa-dev mailing list (Cocoa-dev (AT) lists (DOT) apple.com)
Help/Unsubscribe/Update your Subscription:
%40developershed.com

This email sent to bsdarchive (AT) developershed (DOT) com

May 7, 2006, at 12:03 PM, Todd Blanchard wrote:

This is even a bit restricting since it may not tell you all you
need to know to be compatible. For instance, it may be that the
object subclasses NS but still implements the protocol you
need - so you can call conformsToProtocol: to see if this is true.
If there is a formal protocol defined, this is probably the best
way to check if the object is what you expect.

If you're using a formal protocol, you can also check at compile-
time, by declaring it as part of the type:
-(void)foo: (id<ProtocolName>)bar;

sherm--
Cocoa programming in Perl:
Hire me! My resume: http://www.dot-app.org

Do not post admin requests to the list. They will be ignored.
Cocoa-dev mailing list (Cocoa-dev (AT) lists (DOT) apple.com)
Help/Unsubscribe/Update your Subscription:
%40developershed.com

This email sent to bsdarchive (AT) developershed (DOT) com

May 7, 2006, at 12:56 PM, Lawrence Sanbourne wrote:
5/7/06, Ben Dougall <bend (AT) freenet (DOT) co.ukwrote:
>Todd, thanks for the reply.
>>
>Sunday, May 7, 2006, at 05:03 pm, Todd Blanchard wrote:
>>
>isKClass: I think tests to see if you are a subclass of a
>given
>class. Its what I have used before.
>>
>i'm not after subclasses though -- just is of a particular type or
>not. []
>
-isKClass: actually returns YES if the object is a member of the
given class or is a subclass of the given class. This is probably the
behavior you want,

Ben specifically said he doesn't want the -isKClass: test, and
the code options in his original message are consistent with this.
Since we don't know what the context is, we don't have enough
information to second-guess.

*Assuming* specific class membership is the desired test, offhand I
would use -isMClass: instead of comparing class objects, just
because I think it reads better, but I doubt it makes any practical
difference. Conceivably for debugging it might be useful to break on
-isMClass:, or replace it via +poseAsClass:, but if your
situation is very simple it probably doesn't matter.

Do not post admin requests to the list. They will be ignored.
Cocoa-dev mailing list (Cocoa-dev (AT) lists (DOT) apple.com)
Help/Unsubscribe/Update your Subscription:
%40developershed.com

This email sent to bsdarchive (AT) developershed (DOT) com