Question

I have two additional columns on my PFUser “firstName” and “lastName”. They are saving properly; I can see the data in the data browser.

I have another PFObject “class” that has a property with a NSArray of PFUsers. I use the class method +fetchAllIfNeededInBackground:block: on PFObject to fetch the array of PFUsers. In the callback block, I call objectForKey: on each of the PFUsers in the array, but I access them through the owning PFObject.

// invited is the NSArray of PFUsers
self.whoCell.mainLabel.text = [[self.plan.invited objectAtIndex:0] 
                                                  objectForKey:@"firstName"];

Debugger outputs this at a breakpoint right before the objectForKey call:

(lldb) po self.plan.invited
(NSArray *) $4 = 0x06e62a60 <__NSArrayM 0x6e62a60>(
<PFUser:GCCdPjCU2J> {
    firstName = Fake;
    lastName = Account;
    username = yyajnbafv53qw4yhjm9sfoiis;
}
)

Edit: adding implementation of self.plan.invited because the above is misleading.

- (NSArray*)invited
{
  // self.dataSource is a PFObject*
  return [self.dataSource objectForKey:INVITED_PROP];
}

Yet when the above call it made to objectForKey: this exception is thrown:

'NSInternalInconsistencyException', reason: 'Key "firstName" has no data.  Call fetchIfNeeded before getting its value.'

Edit: Accessing the array of fetchedObjects that is passed to the block callback for +fetchAllIfNeededInBackground doesn’t throw, but accessing the actual array that was originally passed to +fetchAllIfNeededInBackground throws.

Calling fetchIfNeeded before the call solves the problem, but why? The data is already there. Do I miss understand +fetchAllIfNeededInBackground in that it DOES NOT updated the PFObject that owns to collection of PFUsers?

Answer 1

I figured out what was happening. Let me explain with code:

PFQuery *query = [PFQuery queryWithClassName:@"TestClass"];
PFObject *testObj = [query getObjectWithId:@"xWMyZ4YEGZ"];

// an array of PFUser "pointers" (pointers in Parse parlance)
NSLog(@"%@", [testObj objectForKey:@"userArrayProp"]);
[PFObject fetchAll:[testObj objectForKey:@"userArrayProp"]];

// now userArrayProp contains fully fetched PFObjects
NSLog(@"%@", [testObj objectForKey:@"userArrayProp"]);

For me, after a certain amount of time userArrayProp would revert to an array of “pointers” and this mystified me. My problem was that calling refresh on a PFObject will revert a fetched array BACK to an array of pointers. Like this:

PFQuery *query = [PFQuery queryWithClassName:@"TestClass"];
PFObject *testObj = [query getObjectWithId:@"xWMyZ4YEGZ"];

// an array of PFUser "pointers" (pointers in Parse parlance)
NSLog(@"%@", [testObj objectForKey:@"userArrayProp"]);
[PFObject fetchAll:[testObj objectForKey:@"userArrayProp"]];

// now userArrayProp contains fully fetched PFObjects
NSLog(@"%@", [testObj objectForKey:@"userArrayProp"]);

[testObj refresh];

// now userArrayProp contains pointers again :(
NSLog(@"%@", [testObj objectForKey:@"userArrayProp"]);

Wish it said that [PFObject refresh] did that in the documentation….