A query based on 2 other query results - objective-c

Question

EDIT 3: Okay forget the previous edits, I finally figured out it all out! But I still have one small question. The query finds and displays the username of the users who share the same Favourite Foods, and then displays their entire Favourite Food array. My question is, how can I display only the favourite foods that are the same as the current users favourite foods? Code:
PFQuery *query = [PFQuery queryWithClassName:#"_User"];
[query whereKey:#"username" notEqualTo:[PFUser currentUser][#"username"]];
[query whereKey:#"favouriteFood" containedIn:[PFUser currentUser][#"favouriteFood"]];
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
if (!error) {
for (PFObject *object in objects) {
NSString *username = object[#"username"];
NSArray *results = object[#"favouriteFood"];
NSLog(#"Username: %# Shared Favourite Food: %#", username, results);
}
}
else {
NSLog(#"O dang");
}
}];
This displays the user who has atleast 1 common favourite food with the current user, but then displays all of their favourite food, instead of the ones that are common.
Thanks.
First Post:
I'm trying to create a query that gets the result of query1 (an array) for the current user, and then uses query2 to search the database for other accounts that contain one or more of the same data in their array. Here is an example to help understand what I'm trying to do:
Users have the ability to enter data into an array, let's call the array favouriteFoodArray. All data entered into the array is saved to Parse in a row called favouriteFood.
Now, the current user wants to search for other users who share the same favourite food (at least one array entry the same).
So I have query1 to find the current User's favourite food array:
PFUser *currentUser = [PFUser currentUser];
PFQuery *favouriteFood = [PFQuery queryWithClassName:#"_User"];
[favouriteFood whereKey:#"username" equalTo:currentUser.username];
[favouriteFood findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
if (!error) {
for (PFUser *object in objects) {
self.usernameString = object.username;
[self.results arrayByAddingObjectsFromArray:object[#"favouriteFood"]];
NSLog(#"Username: %#, Favourite Food: %#", self.usernameString, self.results);
}
}
else {
NSLog(#"Error..");
}
}];
query2 then goes and finds the favourite food of ALL the users, so we can compare the query1 result with the query2 result and display the usernames of the people that have at least one common array entry:
PFQuery *allFavouriteFood = [PFQuery queryWithClassName:#"_User"];
[allFavouriteFood findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
if (!error) {
for (PFUser *object in objects) {
self.allUsernameString = object.username;
[self.allFavouriteFoodArray arrayByAddingObjectsFromArray:object[#"favouriteFood"]];
NSLog(#"Username: %# Favourite Food: %#", self.allUsernameString, self.allFavouriteFoodArray);
}
}
}];
Now, these 2 queries work, the problem I am having is creating a third query to compare the query1 result with the query2 result. I've tried using:
...
[finalSearch whereKey:#"favouriteFood" containedIn:self.allFavouriteFoodArray];
...
but I get some strange errors. I've been trying to work this out aaaallll day. Any help is greatly appreciated. I hope I haven't over-complicated all of this.
Thank you.
EDIT:
Here's an example for query3:
PFQuery *results = [PFUser query];
[results whereKey:#"favouriteFood" containedIn:self.allFavouriteFoods];
[results findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
if (!error) {
for (PFUser *object in objects) {
self.allUsernameString = object.username;
[self.favouriteFoodResults arrayByAddingObjectsFromArray:object[#"favouriteFood"]];
NSLog(#"Username: %# Shared Favourite Food: %#", self.otherUsernameString, self.allFavouriteFoodArray);
}
}
else {
NSLog(#"Error");
}
}];
I get all sorts of errors when I have whereKey:containIn: self.allFavouriteFoods.
'NSInvalidArgumentException', reason: '*** setObjectForKey: object cannot be nil (key: $in)'.

Answer 1

Your exception 'NSInvalidArgumentException', reason: '*** setObjectForKey: object cannot be nil (key: $in)' means that you haven't actually got a list of food to look for when you make the request. You should call fetchIfNeededInBackgroundWithBlock: on the current user to ensure you have the food list (allFavouriteFoods) available.
Once you have that, i.e. in the completion block, your search for users with any matching foods is correct:
[results whereKey:#"favouriteFood" containedIn:self.allFavouriteFoods];
But you can reference it directly as:
[results whereKey:#"favouriteFood" containedIn:[PFUser currentUser][#"favouriteFood"]];
(assuming that the current user will always have some favourite food when this is run)