Re: Getting all subclasses
Re: Getting all subclasses
- Subject: Re: Getting all subclasses
- From: Mike Abdullah <email@hidden>
- Date: Wed, 18 Jun 2008 17:57:31 +0100
Another option would be to write a +load method in your abstract
superclass that will be automatically called for any subclasses and
register them with the superclass.
Mike.
On 18 Jun 2008, at 16:45, Laurent Cerveau wrote:
Fantastic!
Thanks to you and Omar.
laurent
On Jun 18, 2008, at 9:28 AM, Graham Cox wrote:
If you need a list of subclasses of a class, there isn't a built-in
function - you have to test them one at a time. However I had the
exact same need recently and wrote a little helper class to do it.
One thing I ran into in my situation is that I really needed to
prevent +initialize from ever getting called, because some low-
level classes in the Cocoa framework wrote certain messages to the
log when they were invoked (because they are obsolete and shouldn't
be used) but testing for the class itself was enough to trigger this.
So, my code uses a lower-level function. Here it is:
@interface DKRuntimeHelper : NSObject
+ (NSArray*) allClasses;
+ (NSArray*) allClassesOfKind:(Class) aClass;
@end
@implementation DKRuntimeHelper
+ (NSArray*) allClasses
{
return [self allClassesOfKind:[NSObject class]];
}
+ (NSArray*) allClassesOfKind:(Class) aClass
{
// returns a list of all Class objects that are of kind <aClass>
or a subclass of it currently registered in the runtime. This
caches the
// result so that the relatively expensive run-through is only
performed the first time
static NSMutableDictionary* cache = nil;
if ( cache == nil )
cache = [[NSMutableDictionary alloc] init];
// is the list already cached?
NSArray* cachedList = [cache
objectForKey:NSStringFromClass( aClass )];
if ( cachedList != nil )
return cachedList;
// if here, list wasn't in the cache, so build it the hard way
NSMutableArray* list = [NSMutableArray array];
Class* buffer = NULL;
Class cl;
int i, numClasses = objc_getClassList( NULL, 0 );
if( numClasses > 0 )
{
buffer = malloc( sizeof(Class) * numClasses );
NSAssert( buffer != nil, @"couldn't allocate the buffer");
(void) objc_getClassList( buffer, numClasses );
// go through the list and carefully check whether the class can
respond to isSubclassOfClass: - if so, add it to the list.
for( i = 0; i < numClasses; ++i )
{
cl = buffer[i];
if( classIsSubclassOfClass( cl, aClass ))
[list addObject:cl];
}
free( buffer );
}
// save in cache for next time
[cache setObject:list forKey:NSStringFromClass( aClass )];
return list;
}
@end
BOOL classIsNSObject( const Class aClass )
{
// returns YES if <aClass> is an NSObject derivative, otherwise
NO. It does this without invoking any methods on the class being
tested.
return classIsSubclassOfClass( aClass, [NSObject class]);
}
BOOL classIsSubclassOfClass( const Class aClass, const Class
subclass )
{
Class temp = aClass;
int match = -1;
while(( 0 != ( match = strncmp( temp->name, subclass->name,
strlen( subclass->name )))) && ( NULL != temp->super_class ))
temp = temp->super_class;
return ( match == 0 );
}
hth,
cheers, Graham
On 18 Jun 2008, at 3:19 pm, Laurent Cerveau wrote:
Hi
Is there a way to get all subclases of a class. I have a class
that I would call abstract (although I did not find any real way
to declare some methods as virtual) and would like to get a list
of all "real" subclass implementations.
Thanks
laurent
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