Parse and Core data relation and pointers

Question

i am trying to sync my project to parse. right now i am saving my data in core data. i have 2 kind of entities: Night and Session. it's look like this: Night have many session and session have one night. enter image description here

when i want to add session to night i create or fetch night and add new session. this way i can get from my night all the session and the opposite way. in order to uploading it to parse i have added in the "Session" table "Night" column ( of type Pointer ) and in "Night" table i added "Sessions" column ( of type relation ) this is how it's look like:

enter image description here

i already succeeded to sync all the record from parse to Core data EXCEPT the relation and Pointers. my problem is that the only solution for that ( insert this relation into core data ) is to create new night ( i mean create instance ) and create new sessions and add them like this:

-(void)addSession:(Session *)session toNight:(Night *)night {
    if (session && night) {
        NSMutableSet * sessionSet = [night.sessions mutableCopy];
        [sessionSet addObject:session];
        night.sessions = sessionSet;
    }
}

So my Question is:

this is the only way? create instance and add them?
when i add Session to Night or when i add Night to session, why it's not shown in the DB table. i can not see this connection. ( like i see in parse ,relation and pointers)
when i get the Relation from parse it's look like this:

sessions = { "__type" = Relation; className = Session; };

what i can do with that?

Thanks for reading this long Question and i hope i was clear :)

BTW: i follow this tutorial and they do not have relation and pointers.

Updatde i am using Parse Rest Clint API.

sergio · Accepted Answer · 2014-07-30 09:15:00Z

2

this is the only way? create instance and add them?

yes. either you create a night object and set its sessions property; or you create a session object and set its night property. (provided you have defined and inverse in your core data model).

when i add Session to Night or when i add Night to session, why it's not shown in the DB table. i can not see this connection. ( like i see in parse ,relation and pointers)

this is not clear to me. What would you like to see in the DB table? if you add a bunch of sessions to a night, or you set the night property on session object, then when you inspect those object (reap. night - session) you can access the properties and should show the right value...

when i get the Relation from parse it's look like this:

In Parse, you do not need to model both the Pointer and the Relation (as it happens in Core Data where you have a relation and its inverse).

You just need the pointer for a one to many relationship. Parse relations are used from many to many relationships.

So, what you should to store all of the sessions in Parse is fetching them through a query like:

PFObject* night ...
PFQuery *query = [PFQuery queryWithClassName:@"Sessions"];
[query whereKey:@"night" equalTo:night];

then [query findObjects...] will give you an array of sessions you can add in a go to your Night Core Data object. (so, no need to call multiple time addSession:).

Hope this helps.

edited Jul 30, 2014 at 9:15

answered Jul 30, 2014 at 8:44

sergio

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4 Comments

Sosily Over a year ago

i am using Parse Rest clint API.

sergio Over a year ago

well, my remark holds still even if you are using the REST API. Check parse.com/docs/rest#queries-relational at the Relational Queries section to find the equivalent (you will need to give night objectId explicitly)

Sosily Over a year ago

Thanks for you quick response :) but correct me if i'm wrong, your answer is for my third question, right? "how i get the Relation from parse?"

sergio Over a year ago

You are right, in my mind, the really important question was the third... :-) anyway, I added answers for the other 2 questions...

Sosily · Accepted Answer · 2014-08-13 10:02:05Z

0

This is just answer to my first question: i follow this article and i found this quote:

Core Data cannot operate on data without loading the data into memory.

so i guess i solved my first question. Yes i have to load the data into my memory and then make the connection.

answered Aug 13, 2014 at 10:02

Sosily

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