Parse.com array of pointers or PFRelation

Question

Help me please. I am working with social network app. I want create PFObject "Group". Users can follow it. But only other participants can add other users as members.

As I understand I can develop following feature with PFRelation class. But tell me please, how can I develop feature with adding other users to group?User is protected class so I can't add PFRelation to another user. So only one way adding users to groups by another user is creation array of pointers?

Any thoughts? Thanks

There are two, distinct ideas: array of pointers and relation. For members of a group numbering in the 100k, the only reasonable choice is a relation. — danh
PFRelation is the way to go. Using an Array will make it so slow when making a query. — gagarwal
Thanks, guys. But could I add PFRelation from User1 to User2? PFUser is protected, so I can't add another user without his conformation right? + I can't understand how can I create query where user is participant — Roman
I found this blog.parse.com/2012/05/17/new-many-to-many. So I can do the same queries as with array. Nice — Roman

applequist applequist · Accepted Answer · 2015-03-12T12:34:51

So you want to create a many-to-many relationship between users and groups and only users that are already members of a given group can add a new user to this group right ?

If so here is how I would do it...

Group creation

// Create the group and add its creator as the sole group member
PFUser * user = [PFUser currentUser];
PFObject * group = [[PFObject alloc] initWithClassName:@"Group"];
PFRelation * members = [group relationForKey:@"members"];
[members addObject:user];

// Set an ACL so that the group is visible but only the 
PFACL * acl = [PFACL ACL];
[acl setPublicReadAccess:true];
[acl setWriteAccess:true forUser: user];
group.ACL = cal

Add a new group member

PFUser * member = [PFUser currentUser];
PFUser * candidate = ...; // not yet a member 
PFObject * group = ...; // The group candidate wants to join
PFRelation * members = [group relationForKey:@"members"];
[members addObject:candidate];
[group.ACL setWriteAccess:true forUser:candidate];

In step 2, member is a member of group and so has write access required to add a new user, candidate. After step 2, candidate is now a full member and has gained write access to the group.

However I have not tested this: - Does the relation "inherits" the ACL from the group ? Or anyone that can read the group, can access the relation and then add itself to the group ?

Also it seems hard to distinguish roles among members. I think that now any member could decide to delete the group...

You're probably better off enforcing the rules at application level.

Parse.com array of pointers or PFRelation

1 Answers