#import <objc/runtime.h>

NSArray *ClassGetSubclasses(Class parentClass) {

int numClasses = objc_getClassList(NULL, 0);

Class *classes = NULL;

classes = malloc(sizeof(Class) * numClasses);

numClasses = objc_getClassList(classes, numClasses);

NSMutableArray *result = [NSMutableArray array];

for (NSInteger i = 0; i < numClasses; i++) {

Class superClass = classes[i];

do{

superClass = class_getSuperclass(superClass);

} while(superClass && superClass != parentClass);

if (superClass == nil) {

continue;

}

[result addObject:classes[i]];

}

free(classes);

return result;

} 

注意：objc_getClassList()方法的CPU开支非常大，此方法尽量少用。