CODEWITHSUNDEEP
iosparse-platformpfrelation
cdub
cdub

Reputation: 25711

Understanding and using Parse many to many relations

I have 2 tables in Parse like so:

Users:
(PFUsers table with all Parse data)
belongsToGroups (A Parse Relation to Groups which is many to many)

Groups:
groupId
name
groupMembers (A Parse Relation to Users which is also many to many)

I have the following code:

PFObject *groups = [PFObject objectWithClassName:@"Groups"];
groups[@"name"] = name;
syncUsers[@"isActive"] = [NSNumber numberWithInt:1];
//[groups saveInBackground];

PFUser *current = [PFUser currentUser];
PFRelation *relation = [syncUsers relationforKey:@"groupMembers"];
[relation addObject:current];
[groups saveEventually];

PFRelation *relation2 = [current relationforKey:@"belongsToGroups"];
[relation2 addObject:groups];
[current saveEventually];

First, the top 2 blocks of code work fine, but how do I update the relationship in Users so that I can do View Relation in Parse and see my groups?

Two, do I need to create the Relation in users AND groups so that it can be many to many?

Upvotes: 1

Views: 4092

Answers (2)

CLSource
CLSource

Reputation: 31

First for a relation you need that both objects exist in the Parse Database. Then you must use the PFRelation object and save the object with the relation.

I recommend using CodeCloud for stablishing relationships so you can share the code with Android or Web Apps.

// Objects
PFObject *student = [PFObject objectWithoutDataWithClassName:@"Student" objectId:@"xauj37H"];

PFObject *teacher = [PFObject objectWithoutDataWithClassName:@"Teacher" objectId:@"xJdcj238"];

// Add a student to the teacher object

// Get the students relation
PFRelation *studentsForTeacher = [teacher relationForKey:@"students"];

// Add a student
[studentsForTeacher addObject:student];

// save the teacher, use InBackground instead 
[teacher save];

// Now add a teacher for the student
PFRelation *teachersForStudent = [student relationForKey:@"teachers"];

[teachersForStudent addObject:teacher];

// Save the student
[student save];

// And now you can query the students of a teacher or the teachers of a student

// Students for a Teacher
PFQuery *studentsQuery = [studentsForTeacher query];

[studentsQuery find];

// Teachers for a Student
PFQuery *teachersQuery = [teachersForStudent query];

[teachersQuery find];

Upvotes: 1

Macrosoft-Dev
Macrosoft-Dev

Reputation: 2185

You can use whereKey:equalTo: on a relation column and pass it a PFObject. This query will then return all Teacher objects which have this student in their "students" relation:

PFQuery *query = [PFQuery queryWithClassName:@"Teacher"];
[query whereKey:@"students" equalTo:student];

In this example, the student is a PFObject with a className that matches the relation in "students". If this is a relation of PFUsers and you're looking for the current user's "Teacher"s, you'd use:

PFQuery *query = [PFQuery queryWithClassName:@"Teacher"];
[query whereKey:@"students" equalTo:[PFUser currentUser]];

Upvotes: 1

Related Questions