Parse.com relational query issue

Question

I have the following tables name "aniStudii" and "discipline", I have made a screenshot as well:

enter image description here

As you can see, there is a relation between these tables, at the "materii" column. The row from "aniStudii" with the column "Anul I" has a value and the other column has a different value, values that can be found in the "discipline" table.

I am using this query to get the values, but all I get is Error: bad pointer for key: _p_materii (Code: 106, Version: 1.2.8)

This is my query:

PFQuery *query = [PFQuery queryWithClassName:@"aniStudii"]; //1
PFObject *aniStudiu = [PFObject objectWithClassName:@"discipline"];
[query whereKey:@"materii" equalTo:aniStudiu];

[query findObjectsInBackgroundWithBlock:^(NSArray *results, NSError *error) {
    NSLog(@"%@",results);
}];

Where is the problem? A big thanks in advance.

Wain · Accepted Answer · 2013-05-09 10:48:48Z

2

Do something like this, where you start from a specified object (which you may need a query to find):

PFObject *sourceObject = ...;

PFRelation *relation = [sourceObject relationforKey:@"materii"];

[[relation query] findObjectsInBackgroundWithBlock:^(NSArray *results, NSError *error) {
    NSLog(@"%@",results);
}];

To get the first object you can perform a query something like:

PFQuery *query = [PFQuery queryWithClassName:@"aniStudii"];
[query whereKey:@"numeAn" equalTo:@"######"];

edited May 9, 2013 at 10:48

answered May 9, 2013 at 8:44

Wain

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5 Comments

Carmichael Over a year ago

PFObject *sourceObject = [PFObject objectWithClassName:@"aniStudii"];      PFRelation *relation = [sourceObject relationforKey:@"materii"];          [[relation query] findObjectsInBackgroundWithBlock:^(NSArray *results, NSError *error) {         NSLog(@"%@",results);     }];

And I get

2013-05-09 11:53:40.438 licentaUser[2873:1b03] Error: a valid pointer is needed for RelatedTo operator (Code: 102, Version: 1.2.8) 2013-05-09 11:53:40.440 licentaUser[2873:c07] (null)

Wain Over a year ago

You need an instance of PFObject which has been retrieved from the server. You can't just create a new instance (which is what objectWithClassName does) and then query the relation.

Carmichael Over a year ago

PFQuery *query = [PFQuery queryWithClassName:@"aniStudii"]; PFObject *sourceObject = [query getObjectWithId:@"xWMyZ4YEGZ"]; PFRelation *relation = [sourceObject relationforKey:@"materii"]; [[relation query] findObjectsInBackgroundWithBlock:^(NSArray *results, NSError *error) { NSLog(@"%@",results); }]; This works, but I have to know the objectId to make the result happen. I don't want that, is there anyway to go around this?

Wain Over a year ago

You can query for the source object by name or creation date (or any other field it has). Or, you can query for all instances of a particular object (paginated) and display them for the user to choose...

Carmichael Over a year ago

query hasn't got any other options besides getObjectWithId. So instead of ` PFObject *sourceObject = [query getObjectWithId:@"xWMyZ4YEGZ"];` I don't know what else to use.

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