Parse.com-查找已删除的对象

Question

I have an iOS app that synchronises to Parse.com.

It can find anything that was added to Parse and add it to Core Data using PFQuery. It can also check for any data that has been updated and update accordingly.

However, I'm not sure how to find objects that have been deleted on Parse.com.

Does anyone know of a query that will list the ObjectIDs that have been deleted and the date of their deletion? I can then remove them from the Core Data on the app.

Answer 1

I needed this function, too, but figured that marking rows as deleted will bloat the data and add a condition to every query. So I created a Deletion class. It records only the class name and ID of any deleted row, so it stays pretty small:

function recordDeletion(klass, identifier) {
    var Deletion = Parse.Object.extend("Deletion");
    var deletion = new Deletion();
    deletion.set("klass", klass);
    deletion.set("identifier", identifier);
    return deletion.save();
}

// for every class that you want deletions recorded, add one of these...
Parse.Cloud.beforeDelete("MyClass", function(request, response) {
    recordDeletion("MyClass", request.object.id).then(function() {response.success();});
});

My iOS clients record the date when they last fetched data, then get everything newly created/updated from MyClass (+ others) and Deletion . With that, the can delete the Deletions locally.

Over a longer period, the clients remove all of the locally cached data and get a fresh copy of everything (except Deletions). This allows me to have a scheduled job on the server that will empty the Deletion table (on a cycle that's much longer than the client's cycle).

Answer 2

There is no provided API for this.

As per the comment from @Fogmeister you can tag objects as deleted and update like that. Alternatively you can maintain a specific list of deleted ids (potentially using Parse.Cloud.beforeDelete ) and then make a specific request to get only the deletions.

In either case you will need to explicitly manage the scheme you choose and also decide how and when to clean up the deleted objects / deletion records.