Return object data from parse object query callback

Question

I am quite new to Java/android programming and I'm stuck at the Parse.com callback.

In have a method (method1) that requests the objectId of an object owned by the current user. It does this by calling upon another method (method2) that contains a query which pulls an object from the data browser with a callback.

I managed to write all code but I'm stuck at the callback for method 2. I want the object data to be returned to method 1 but this seems to be inpossible because of the Callback type (void).

I also do now know how to let the rest of the method wait for the callback to return before executing.. I would appreciate it if anyone could help me out.

This is my code:

public void method1(){
    String objectId = null;

    objectId = QueryStatisticObjectId("Age");

    Log.i(TAG, "objectId returned to method = " + objectId);
}



    public String QueryStatisticObjectId(final String statistic){
        ParseQuery<ParseObject> query = ParseQuery.getQuery("Statistics");
        query.whereEqualTo("user", ParseUser.getCurrentUser());
        query.whereEqualTo("statistic", statistic);
        query.getFirstInBackground(new GetCallback<ParseObject>() {
            @Override
            public void done(ParseObject object, ParseException e) {
                if (e == null){
                    //We have data!
                    String objectId = object.getObjectId();
                    return;
                }
                else
                {
                    //Something went wrong!?!
                    e.printStackTrace();
                }
            }
        });

mbm29414 · Accepted Answer · 2015-01-11 21:21:26Z

2

So, what you're trying to do isn't available using Parse in iOS or Android. I think it will probably work the way you want on .NET (using the Await keyword).

Instead, ask yourself:

Why do you want to architect your class in this way?
Why is it important to return the value to the original method?
Is it just because you want a method that is recyclable?
Is it because you want to handle the value in a method context that makes more sense?

If so, try something like this:

public void method1() {
    QueryStatisticObjectId("Age", new GetCallback<ParseObject>() {
        @Override
        public void done(ParseObject object, ParseException e) {
            if (e == null) {
                String objectId = object.getObjectId();
                Log.i(TAG, "objectId returned to method = " + objectId);
            } else {
                Log.i(TAG, "objectId not found");
            }               
        }
    });
}

public void QueryStatisticObjectId(final String statistic, GetCallback<ParseObject> callback) {
    ParseQuery<ParseObject> query = ParseQuery.getQuery("Statistics");
    query.whereEqualTo("user", ParseUser.getCurrentUser());
    query.whereEqualTo("statistic", statistic);
    query.getFirstInBackground(callback);
}

In this way, you can write the code to handle the returned result in the context (method1()) that makes sense, while also re-using the query method as much as you like. Additionally, as opposed to @JimW's answer, this doesn't utilize synchronous web calls, which will also afford you the opportunity to keep your app's UI responsive.

answered Jan 11, 2015 at 21:21

mbm29414

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1 Comment

Dannyvdz Over a year ago

Looks like this is what I was looking for. Need to get some sleep now but I'll be sure to dig in and implement this in my app tomorrow. Thanks a lot!

user2097310 · Accepted Answer · 2015-10-22 04:27:47Z

0

I am having the same issue, the callbacks are really annoying, seems like they fire randomly, and the return type of void makes Overriding everything neccessary. I solved your problem by using regular .find() without the callback. I then did all the grunt work using custom code.

answered Oct 22, 2015 at 4:27

user2097310

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