All Classes Conforming to Protocol

allClassesConformingToProtocol.h

#import <Foundation/Foundation.h>

NSArray* allClassesConformingToProtocol(Protocol* p); // fwd dec; makes compiler stfu

allClassesConformingToProtocol.m

#import "allClassesConformingToProtocol.h"

#include <objc/runtime.h>

NSArray* allClassesConformingToProtocol(Protocol* p)
{
    NSMutableArray* arr = [NSMutableArray array];
    int numClasses = objc_getClassList(NULL, 0);
    Class* allClasses=(Class*)malloc(sizeof(Class*)*numClasses);
    objc_getClassList(allClasses, numClasses);
    for (size_t i=0;
         i<numClasses;
         ++i)
        if (class_conformsToProtocol(allClasses[i], p))
            [arr addObject:allClasses[i]];
    free(allClasses);
    return arr;
}