Memory leak while handling Foundation Object from NSJSONSerialization - objective-c

Question

I'm struggling to fix a memory leak in a helper function I have made. The helper function takes the result of
+ (id)JSONObjectWithData:(NSData *)data options:(NSJSONReadingOptions)opt error:(NSError * _Nullable *)error
and converts all the leaf elements into NSStrings if they are NSNumbers.
Here is the method:
-(NSArray *) stringisizeObjects:(NSArray *)inputArray{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
NSMutableArray *mutable = [[NSMutableArray alloc] initWithCapacity:[inputArray count]];
for (int i = 0; i < [inputArray count]; i++) {
NSArray *keys = [inputArray[i] allKeys];
NSMutableDictionary *addDictionary = [[NSMutableDictionary alloc] initWithCapacity:[keys count]];
for (int j = 0; j < [keys count]; j++) {
id theObject = [[inputArray[i] objectForKey:keys[j]]autorelease];
if ([theObject isKindOfClass:[NSNumber class]]) {
[addDictionary setObject:[theObject stringValue] forKey:keys[j]];
[theObject release];
}else if ([theObject isKindOfClass:[NSString class]]){
[addDictionary setObject:[inputArray[i] objectForKey:keys[j]] forKey:keys[j]];
}
}
[mutable addObject:addDictionary];
}
NSArray *returnArray = [mutable copy];
[mutable removeAllObjects];
[mutable release];
[pool drain];
return returnArray;
}
Here is how I get the input array.
id parsedThingy = [NSJSONSerialization JSONObjectWithData:resultJSONData options:1 error:&jsonDecodeError];
Before I can pass the result to my stringisize method I must ensure that I have an NSArray of NSDictionaries with matching keys.
NSArray *resultArray = [self stringisizeObjects:parsedThingy];
The X-Code memory leaks tool has pointed me to this method as the cause of my problem.
Instruments showing leaks
As you can see I have tried wrapping things in autorelease pools, autoreleasing and releasing. I just don't see any way forward here.
This is a non ARC project that runs 24/7.
Edit: I took the advice from Droppy and tried to re-write the method using mutableCopy. The leak is still there. At this point my only work around maybe to change the source of the JSON to send only strings. :(
-(NSArray *) stringisizeObjects2:(NSArray *)inputArray{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
NSMutableArray *mutableArray = [inputArray mutableCopy];
for (int i = 0; i < [mutableArray count]; i++) {
NSMutableDictionary *mutableDict = [mutableArray[i] mutableCopy];
NSArray *keys = [mutableDict allKeys];
for (int j = 0; j < [keys count]; j++) {
if ([[mutableDict objectForKey:keys[j]] isKindOfClass:[NSNumber class]]) {
NSString *stringValue = [[mutableDict objectForKey:keys[j]] stringValue];
[mutableDict removeObjectForKey:keys[j]];
[mutableDict setObject:stringValue forKey:keys[j]];
}
}
mutableArray[i] = [mutableDict copy];
[mutableDict release];
}
NSArray *returnArray = [mutableArray copy];
[mutableArray release];
[pool drain];
return returnArray;
}

Answer 1

problem:
addDictionary called alloc but not call release or autorelease
returnArray = [mutable copy]; // did increase retainCount +1, need autorelease here
id theObject = [inputArray[i] objectForKey:keys[j]]; // not need autorelease or release for object that You not own
add NSAutoreleasePool to top an bottom here just do nothing
solution:
-(NSArray *) stringisizeObjects:(NSArray *)inputArray{
NSMutableArray *mutable = [[NSMutableArray alloc] initWithCapacity:[inputArray count]];
for (int i = 0; i < [inputArray count]; i++) {
NSArray *keys = [inputArray[i] allKeys];
NSMutableDictionary *addDictionary = [[NSMutableDictionary alloc] initWithCapacity:[keys count]];
for (int j = 0; j < [keys count]; j++) {
id theObject = [inputArray[i] objectForKey:keys[j]]; // not need autorelease
if ([theObject isKindOfClass:[NSNumber class]]) {
[addDictionary setObject:[theObject stringValue] forKey:keys[j]];
//[theObject release]; // not need release value here
}else if ([theObject isKindOfClass:[NSString class]]){
[addDictionary setObject:[inputArray[i] objectForKey:keys[j]] forKey:keys[j]];
}
}
[mutable addObject:addDictionary];
[addDictionary release]; // release after not use
}
NSArray *returnArray = [[[NSArray alloc] initWithArray:mutable] autorelease]; // auto release for return value
[mutable removeAllObjects];
[mutable release];
return returnArray;
}