I have a class named Circle with a relation named "members" to the _User class.
Class Circle:
Class _User:
I'm trying to query all Circles that the current user belongs to (inside the "members" relations).
PFUser *user = [PFUser currentUser];
PFRelation *relation = [user relationForKey:#"members"];
PFQuery *query = [relation query];
[query findObjectsInBackgroundWithBlock:^(NSArray *PF_NULLABLE_S objects, NSError *PF_NULLABLE_S error){
//objects size here is 0
//error is nil
}];
The problem is that the NSArray is empty and no error is received into the block.
One solution I'm thinking of is creating an actual table to store this relation and have a Relation column in both Circle and _User, but I believe there should be a better way to do this.
It doesn't appear that user has a members col. So, asking a user for its members relation is sure to fail. You want to query Circle...
PFQuery *query = [PFQuery queryWithClassName:#"Circle"];
[query whereKey:#"members" equalTo:user];
Related
If I have pointers to multiple _User objects in an array, can i query for a value of a User.
Ex.
I have a class Groups with an array members.
members = [user1, user2, user3].
Can I do something like:
PFQuery *query = [PFQuery queryWithClassName:#"Groups"];
[query whereKey:#"members.name" isEqual:#"James"];
This can be accomplished with a nested query. Create an "innerQuery" to find Users matching the criteria. Then constrain a Group query with whereKey:matchesQuery:.
PFQuery *innerQuery = [PFUser query];
// note that referring to the "name" field only makes sense if you've
// added a name field to User (you might mean username here)...
[innerQuery whereKey:#"name" isEqual:#"James"];
// now the main query is setup to match the innerQuery
PFQuery *query = [PFQuery queryWithClassName:#"Groups"];
[query whereKey:#"members" matchesQuery:innerQuery];
[query findObjectsInBackgroundWithBlock:^(NSArray *comments, NSError *error) {
}];
I have the following query:
PFObject *photoData = [PFObject objectWithClassName:#"Photos"];
PFRelation *relation = [photoData relationForKey:#"photo"];
PFQuery *query = [PFQuery queryWithClassName:#"People"];
query = [relation query];
[query whereKey:#"deleted" equalTo:#NO];
[query whereKey:#"createdAt" lessThan:_createdAt];
[query orderByDescending:#"createdAt"];
query.limit = 20;
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
...
}
I have a database table in Parse called People. In that table, there is a bunch of data but has a relation called photo. Now, I am saving one photo (with its data) in the photo relation. In the Parse dashboard, the data is saved correctly.
How do I fetch that back? Right now I have constraints on this system (and question) that each People objects has ONLY one photo object. So I need to fetch it all back at once.
Relation is just what its literal meaning is. It does not contain any data. If you want to query the data, you need to get the PFQuery from PFRelation by query method like so:
PFRelation *relation = [photoData relationForKey:#"photo"];
PFQuery *photoQuery = [relation query];
// perform your photoQuery here
If you limit them by one object only, then you can change your photo as Pointer type instead of using Relation.
I am using parse to develop an iOS app.
For the database, I have three tables, named user, UserAndCourse, and course.
Where UserAndCar stores a pointer to user and course.
the tables looks like:
My problem is:
How can I query the courses that belongs to the current user on iOS. i.e that look into UserAndCourse to find the rows that user column is current user and query for the course object that is pointed to by the course column.
Can I do this in a single relational query? or I have to query the UserAndCourse table rows first and then query the course it pointed to.
I suggest to use PFRelation, that way you don't need to create new table for relations like userAndCourse. Parse automatically will link through the relation. You just need to create relation between them and do what you want.
Saving relation;
PFUser *user = [PFUser currentUser];
PFRelation *relation = [user relationForKey:#"course"];
[relation addObject:coursePFObject];
[user saveInBackground];
And query when you need to reach them;
PFRelation *relation = [user relationForKey:#"course"];
PFQuery *query = [relation query];
[query findObjectsInBackgroundWithBlock:^(NSArray *results, NSError *error) {
// results contains all the people who subscribe to course
}];
Moreover you can specify your course by adding more queries on it;
PFQuery *query = [relation query];
[query whereKey:#"name" equalTo:#"Math"];
[query findObjectsInBackgroundWithBlock:^(NSArray *results, NSError *error) {
// results contains all the people who subscribe Math course
}];
I think it's better way to shape your tables in parse. Otherwise you need to create table for each relation.
Hope it helps also if you need more detail this can be helpful.
I am writing an iOS app and I am using Parse to store data on the server side.
I have Users and each user can have a Car.
I am trying to figure out how to write a query that allows me to get all users that have a car with year less than 2000 and with a certain color (lets say red).
Each car has a relationship to the user and each user also has a relationship to their car.
User <-> Car (one to one)
I started using the PFQuery:
PFQuery * userQuery = [PFQuery queryWithClassName:#"User"];
I am not sure how to handle the relationship in the query. So, I'm pretty much not sure how to get this done.
Any suggestion?
First off, the User class is a special case, when using it in a query you need to do this:
PFQuery *query = [PFUser query];
Next, the way you construct the query you want depends where the pointer is. If the User has a car property that is a pointer to the Car then the query would be as follows:
PFQuery *userQuery = [PFUser query];
PFQuery *carQuery = [PFQuery queryWithClassName:#"Car"];
[carQuery whereKey:#"year" lessThan:#(2000)];
[carQuery whereKey:#"color" equalTo:#"red"];
[userQuery whereKey:#"car" matchesQuery:carQuery];
[userQuery includeKey:#"car"]
[userQuery findObjectsInBackgroundWithBlock:^(NSArray *users, NSError *error) {
for (PFObject *user in users) {
PFObject *car = user[#"car"];
// read user/car properties as needed
}
}];
If instead the Car class has a user property you just do a normal query and add the following line to let you access the full User object:
[carQuery includeKey:#"user"];
What does your table look like? If you have User as a column in your Car table, you can just query the car table for cars of year less than 2000 and then you would just access the User property of that query. It would look something like this:
PFQuery *carQuery = [PFQuery queryWithClassName:#"Car"];
[carQuery whereKey:#"year" lessThan:#(2000)];
[carQuery includeKey:#"user"];
[carQuery findObjectsInBackgroundWithBlock:^(NSArray *cars, NSError *error) {
if (!error) {
for (Car *car in cars) {
User *user = car#["user"];
}
}
}];
I have 2 classes: PFUser and Groups. In "Groups" class I have all my groups and each group has a relation key called "Members". "Members" holds a list of users related to current group.
How do I query for "Members" key so it returns an array of users?
I've done similar query in past for User related relations, but then I just passed in PFRelation *friendsRelation = [PFUser currentUser] objectForKey:#"friendsRelation"] into query.
This time can't get it to work.
The closest I've come is :
PFQuery *query = [PFQuery queryWithClassName:#"Groups"];
[query whereKey:#"Members" equalTo:[PFUser currentUser]];
[query orderByAscending:#"username"];
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {…}
p.s. Each user has his group(PFObject) added as a key.
How to do a PFRelation query for custom Class:
//1. Get objectID for object from custom class. Previously added as a key for user.
PFObject *currentGroup = [[PFUser currentUser] objectForKey:#"Group"];
//2. Set relation key for which to do the query.
PFRelation *relation = [currentGroup relationForKey:#"Members"];
PFQuery *membersQuery = [relation query];
//Do the query!
[membersQuery findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {}];
There's no need to define for which class to do the query. ObjectIDs are unique.
Hope this will help someone.
If I understood your issue correctly, you want to have an array of « Members » in the same « Group » .
Your query is related to the class « Groups », it should be « Members » instead. You shouldn’t look for « members » equals to [PFUser currentUser], because it will always return only one item in the best case : the PFUser linked with your iPhone/iPad.
If your users has a group key (let’s name it « OwnerGroup » ), then you can try :
PFQuery *membersQuery = [PFQuery queryWithClassName:#"Members"];
[membersQuery whereKey:#"OwnerGroup" equalTo:currentGroup];
[membersQuery orderByAscending:#"username"];
[membersQuery findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {…}