[self.rules enumerateKeysAndObjectsUsingBlock:^(NSString * _Nonnull key, MTRule * _Nonnull obj, BOOL * _Nonnull stop) {
            if (rule.selector == obj.selector
                && mt_object_isClass(rule.target)
                && mt_object_isClass(obj.target)) {
                Class clsA = rule.target;
                Class clsB = obj.target;
                shouldApply = !([clsA isSubclassOfClass:clsB] || [clsB isSubclassOfClass:clsA]);
                *stop = shouldApply;
                NSCAssert(NO, @"Error: %@ already apply rule in %@. A message can only have one rule per class hierarchy.", NSStringFromSelector(obj.selector), NSStringFromClass(clsB));
            }
        }];

  // check if subclass has hooked!
    for (Class clsHooked in MTEngine.defaultEngine.classHooked) {
        
        if (clsHooked != cls && [clsHooked isSubclassOfClass:cls]) {
            NSLog(@"Sorry: %@ used to be applied, can't apply it's super class %@!", NSStringFromClass(cls), NSStringFromClass(cls));
            return NO;
        }
    }

- (BOOL)applyRule:(MTRule *)rule
{
    pthread_mutex_lock(&mutex);
    MTDealloc *mtDealloc = [rule mt_deallocObject];
    [mtDealloc lock];
    __block BOOL shouldApply = YES;
    if (mt_checkRuleValid(rule)) {
        for (id target in [[self.targetSELs keyEnumerator] allObjects]) {
            if (target == rule.target) {
                shouldApply = NO;
                continue;
            }
            NSMutableSet *selectors = [self.targetSELs objectForKey:target];
            for (NSString *selectorName in selectors) {
                if (sel_isEqual(rule.selector, NSSelectorFromString(selectorName))
                    && mt_object_isClass(rule.target)
                    && mt_object_isClass(target)) {
                    Class clsA = rule.target;
                    Class clsB = target;
                    shouldApply = !([clsA isSubclassOfClass:clsB] || [clsB isSubclassOfClass:clsA]) && shouldApply;
                    NSLog(@"Sorry: %@ already apply rule in %@. A message can only have one rule per class hierarchy.", selectorName, NSStringFromClass(clsB));
                }
            }
        }
        shouldApply = shouldApply && mt_overrideMethod(rule);
        if (shouldApply) {
            [self addSelector:rule.selector onTarget:rule.target];
            rule.active = YES;
        }
    }
    else {
        shouldApply = NO;
    }
    [mtDealloc unlock];
    pthread_mutex_unlock(&mutex);
    return shouldApply;
}

MTRule *debounceRule = [[MTRule alloc] initWithTarget:self selector:@selector(updateDebounceString:) durationThreshold:2];
debounceRule.mode = MTPerformModeDebounce;
[debounceRule apply];
NSLog(@"%@", [self mt_allRules]);

MTRule *throttleRule = [[MTRule alloc] initWithTarget:self selector:@selector(updateThrottlingString:) durationThreshold:2];
throttleRule.mode = MTPerformModeLast;
[throttleRule apply];

NSLog(@"%@", [self mt_allRules]);

- (BOOL)applyRule:(MTRule *)rule
{
    pthread_mutex_lock(&mutex);
    __block BOOL shouldApply = YES;
    if (mt_checkRuleValid(rule)) {
        [self.rules enumerateKeysAndObjectsUsingBlock:^(NSString * _Nonnull key, MTRule * _Nonnull obj, BOOL * _Nonnull stop) {
            if (rule.selector == obj.selector
                && mt_object_isClass(rule.target)
                && mt_object_isClass(obj.target)) {
                Class clsA = rule.target;
                Class clsB = obj.target;
                shouldApply = !([clsA isSubclassOfClass:clsB] || [clsB isSubclassOfClass:clsA]);
                *stop = shouldApply;
                NSCAssert(NO, @"Error: %@ already apply rule in %@. A message can only have one rule per class hierarchy.", NSStringFromSelector(obj.selector), NSStringFromClass(clsB));
            }
        }];
        
        if (shouldApply) {
            self.rules[mt_methodDescription(rule.target, rule.selector)] = rule;
            mt_overrideMethod(rule.target, rule.selector);
        }
    }
    pthread_mutex_unlock(&mutex);
    return shouldApply;
}

- (IBAction)tapFoo:(UIButton *)sender {
    [self mt_limitSelector:_cmd oncePerDuration:0.5];
}

Crashed: Thread
0  libsystem_kernel.dylib         0x180f1d2e0 __pthread_kill + 8
1  libsystem_pthread.dylib        0x1810be288 pthread_kill$VARIANT$mp + 376
2  libsystem_c.dylib              0x180e8bd0c abort + 140
3  libsystem_malloc.dylib         0x180f55838 szone_size + 634
4  CoreFoundation                 0x181362c54 -[__NSArrayM insertObject:atIndex:] + 380
5  CoreFoundation                 0x1813aca8c -[NSInvocation retainArguments] + 212
6  MessageThrottle                0x1025e85a0 mt_forwardInvocation + 1916
7  CoreFoundation                 0x18149c2d4 ___forwarding___ + 624
8  CoreFoundation                 0x18138241c _CF_forwarding_prep_0 + 92
9  AllInOne                       0x102adab84 -[CoreData_3_$Lambda$3 lWithId:] + 84
10 ··· ···