This worked well (after a little tweaking!) thanks - got the whole
caboodle running now. I note that NSObject's superclass is NULL, so I
had to switch the order of the while() test in order to correctly
detect plain NSObjects (admittedly this will probably never be needed
in practice).
Here's my implementation (including objective C 2.0 variant), for
anyone's further use:
@implementation MyRuntimeHelper
+ (NSArray*) allClassesOfKind:(Class) aClass
{
// returns a list of all Class objects that return YES to
isKindOfClass:<aClass> currently registered in the runtime
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 );
for( i = 0; i < numClasses; ++i )
{
cl = buffer[i];
if( classIsSubclassOfClass( cl, aClass ))
[list addObject:cl];
}
free( buffer );
}
//NSLog(@"classes: %@", list);
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;
#ifndef __OBJC2__
while(( 0 != ( match = strncmp( temp->name, subclass->name,
strlen( subclass->name )))) && ( NULL != temp->super_class ))
temp = temp->super_class;
#else
while(( 0 != ( match = strncmp( class_getName( temp ),
class_getName( subclass ), strlen( class_getName( subclass ))))) &&
( NULL != class_getSuperclass( temp )))
temp = class_getSuperclass( temp );
#endif
return ( match == 0 );
}
On 27 Mar 2008, at 4:11 pm, Sherm Pendley wrote:
On Thu, Mar 27, 2008 at 12:43 AM, Graham Cox
<[EMAIL PROTECTED]> wrote:
I have a class that can contain different objects which all derive
from a class R. The container can accept instances of any subclass
of R.
Each subclass of R implements a CLASS method for a particular feature,
returning an array. The container needs to build an array which is the
union of all the arrays returned by each subclass. Thus it needs to
iterate through a list of all possible subclasses of R, combining the
arrays as it goes. Problem is that not all possible subclasses of R
are known until runtime, so I need a way to be able to get hold of
such a list, based on the fact that they all inherit from R. Note that
these are not instances of R, but classes. (I can get a list of
instances I have right now, but that doesn't cover the possibility of
another object instance derived from R being added after I already
built the array).
Hope this makes sense - any ideas?
You're on the right track, IMHO. What I would do is climb the
inheritance tree for each registered class. If you find an ancestor
with the name of R, the class you're checking is a subclass. If you
get to a root class (i.e. a class whose super_class member is NULL),
then it's not.
while( NULL != aClass->super_class && 0 != strncmp(aClass->name,
"R", 1) )
aClass = aClass->super_class;
BOOL isSubclassOfR = (NULL != aClass->super_class) ? YES : NO;
Keep in mind that this is for the ObjC 1 runtime. I haven't yet
looked at the ObjC 2 runtime in any detail, so if you're targeting
64-bit Leopard, YMMV.
sherm--
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