如何在课堂上获取Parse.com对象计数

Question

I want to get the object count from 5 classes in Parse.com (to check if all objects were fetched successfully).

Because I'm using findObjectsInBackgroundWithBlock : sometimes not all the objects are fetched before I'm using it, that's why I want to check.

How can I do that?

Answer 1

Update 2 : just noticed you were asking about iOS. its basically the same principle, use fetchAllIfNeeded like so: https://parse.com/docs/ios/api/Categories/PFObject(Synchronous).html#/c:objc(cs)PFObject(cm)fetchAllIfNeeded :

Update : a better way than the naive one (below) would probably be using fetchAllIfNeededInBackground:

ArrayList<ParseObject> objectsToFetch = new ArrayList<>();
objectsToFetch.add(object1);
objectsToFetch.add(object2);
objectsToFetch.add(object3);
ParseObject.fetchAllIfNeededInBackground(objectsToFetch, new FindCallback<ParseObject>() {
    @Override
    public void done(List<ParseObject> objects, ParseException e) {
        //all are fetched, do stuff
    }
});

My native way of doing this is adding an outer boolean array where each boolean is responsible for one of the classes. When a findObjectsInBackgroundWithBlock's 'done' function runs, I set that boolean to "true" and run a function that checks whether all array is true, if so -> all classes have been fetched and I can continue.

example from my code:

boolean[] itemFetched;

protected void getAllClassesAndDoStuffWithThem() {
    itemFetched= new boolean[NUM_OF_CLASSES];

    for (int i=0;i<NUM_OF_CLASSES;i++){
        final int finalI = i;
        itemFetched[i] = false;
        parseObjectArray[i].fetchIfNeededInBackground(new GetCallback<ParseObject>() {
            @Override
            public void done(ParseObject object, ParseException e) {
                itemFetched[finalI] = true;
                finishInitIfPossible();
            }
        });
    }


}

private void finishInitIfPossible() {
    for (int i=0;i<NUM_OF_CLASSES;i++){
        if (!itemFetched[i])
            return;
    }

    //all classes fetched
    finishInit();
}

private void finishInit() {
    //do stuff with all 5 classes
}