PFObject fetchInBackgroundWithBlock returns nil for fetched object

[iosdev-republicofapps]

I used to have code like the following that worked perfectly, without fail, in Parse OS X SDK version 1.6.3, but now fails every single time in Parse OS X SDK version 1.8.1:

PFObject object = ...; // Some object from the cloud

// Make some local changes to object ...

[object saveInBackgroundWithBlock:^(BOOL succeeded, NSError *error) {
  if (succeeded) {
    [object fetchInBackgroundWithBlock:^(PFObject *fetched, NSError *error) {
       // In Parse OS X SDK version 1.6.3 fetched was always non-nil.
       // In Parse OS X SDK version 1.8.1 fetched is always nil.
    }
  }
}];

So fetchInBackgroundWithBlock now always returns nil for an object that originally came from the cloud and definitely exists. Why is it returning nil all of a sudden now? None of my code has changed ... This is definitely a new bug in the Parse OS X SDK.

This is a blocking bug for me.

[nlutsenko]

Hey @iosdev-republicofapps, I've seen this happening yesterday and there was a #104 that fixes the similar problem to what you are describing.
Workaround: Keep the pointer to an object for the entire lifetime of it, since the bug was with evicting the object from memory too early.

I am going to close out this issue, feel free to reopen though if #104 didn't help or if you think there is something else here missing.

[parse-github-bot]

Thank you for your feedback. We prioritize issues that have clear and concise repro steps. Please see our Bug Reporting Guidelines about what information should be added to this issue.

In addition, you might find the following resources helpful:

• Documentation: https://www.parse.com/docs
• Google Groups: https://groups.google.com/forum/#!forum/parse-developers
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[iosdev-republicofapps]

Thanks @nlutsenko I appreciate your rapid response! :-)

What do you mean "keep the pointer to an object for the entire lifetime of it"? The problem is, when I create an object client side and save it to the Parse cloud, I have cloud code that adds extra fields (server side, for security) so I need to immediately fetch the saved object.

For example:

PFObject *object = [PFObject objectWithClassName:@"Foo"];
object[@"bar"] = @"baz";

[object saveInBackgroundWithBlock:^(BOOL succeeded, NSError *error) {
  if (succeeded) {
    // object was created in cloud, and cloud beforeSave added some extra fields
    // cloud-side for security, so we need to retrieve the just-created object again here
    [object fetchInBackgroundWithBlock:^(PFObject *fetched, NSError *error) {
       // In Parse OS X SDK version 1.6.3 fetched was always non-nil.
       // In Parse OS X SDK version 1.8.1 fetched is always nil.
    }
  }
}];

I don't understand how your proposed fix would work - the problem is not that object is nil, the problem is that fetched is nil, so I never get a chance to store a pointer to fetched.

How about this fix:

PFObject *object = [PFObject objectWithClassName:@"Foo"];
object[@"bar"] = @"baz";

[object saveInBackgroundWithBlock:^(BOOL succeeded, NSError *error) {
  if (succeeded) {
    // object was created in cloud, and cloud beforeSave added some extra fields
    // cloud-side for security, so we need to retrieve the just-created object again here
    PFQuery *query = [PFQuery queryWithClassName:@"Foo"];
    [query getObjectInBackgroundWithId:object.objectId block:^(PFObject *queryFetched, NSError *error)  {
        // Will queryFetched be non-nil here?
    }
  }
}];

Would this approach? Trying to query for the refreshed object by id? Maybe queryFetched won't be nil?

Also, when will your fix #104 make it into a release? :-)

Thanks and please advise!

Best,

Joel

[nlutsenko]

That approach would work. Or something like this should also work:

PFObject *object = [PFObject objectWithClassName:@"Foo"];
object[@"bar"] = @"baz";

[object saveInBackgroundWithBlock:^(BOOL succeeded, NSError *error) {
  if (succeeded) {
    // object was created in cloud, and cloud beforeSave added some extra fields
    // cloud-side for security, so we need to retrieve the just-created object again here
    [object fetchInBackgroundWithBlock:^(PFObject *fetched, NSError *error) {
       // In Parse OS X SDK version 1.6.3 fetched was always non-nil.
       // In Parse OS X SDK version 1.8.1 fetched is always nil.
       // Use an `object` here somewhere.
       object;
    }
  }
}];

Since #104 is already merged - you can use it via Cocoapods by adding:
pod 'Parse', :git => 'https://github.com/ParsePlatform/Parse-SDK-iOS-OSX.git'
Or even building the framework for yourself from source using instructions on README.

[iosdev-republicofapps]

Thanks again @nlutsenko .

But in your example above, inside the completion block supplied to fetchInBackgroundWithBlock, will object be the updated version (i.e. [object isEqual:fetched]) or will object be the original version before I saved it? I need the updated version from the server since cloud code added some fields in beforeSave.

Will your trick prevent fetched from becoming nil somehow?

Also, if I go back to using CocoaPods now, will code signing work? I had previously tried using the OS X SDK through CocoaPods but the code signing failed so I had to drop the frameworks in as embedded binaries. Or will code signing just work now because now the pod compiles from source whereas before the pod included pre-compiled libs?

Thanks again and best wishes! :-)

[iosdev-republicofapps]

Are you planning to do another release with this bug fix?

Thanks!

[nlutsenko]

Yup, soon after this weekend and a holiday (it's Labor Day holiday here in US).

[iosdev-republicofapps]

Thanks @nlutsenko , that sounds great! Have a good long weekend. :-)