Add EventuallyQueue API

[dplewis]

Closes: #1230

This is a similar feature to the iOS SDK EventuallyQueue to allow a user to cache objects to be saved later. Inspired by @francimedia repo.

This has a lot of room for improvement, any feedback is appreciated.

• Save internal unique hash on object to the DB to ensure operations won't be duplicated.
• If the operation happens at a later time update object internal state
• Change Polling setInterval to setTimeout?

Parse.Object

Saves / Deletes this object to the server at some unspecified time in the future, even if Parse is currently inaccessible.

Use this when you may not have a solid network connection, and don't need to know when the save completes.
If there is some problem with the object such that it can't be saved, it will be silently discarded.

Objects saved / deleted with this method will be stored locally in an on-disk cache until they can be delivered to Parse.
They will be sent immediately if possible. Otherwise, they will be sent the next time a network connection is
available. Objects saved this way will persist even after the app is closed, in which case they will be sent the
next time the app is opened / SDK is initialized.

await object.saveEventually(options);
await object.destroyEventually(options);

Advance API

Add Object to Queue

Adding unique hashes to your objects is highly recommended

const object = new Parse.Object('TestObject');
object.save({ hash: 'unique' });

await Parse.EventuallyQueue.save(object, options);
await Parse.EventuallyQueue.destroy(object, options);

Send Queue to Parse Server

await Parse.EventuallyQueue.sendQueue();

You can send the queue either right after adding an object or on connect (or other events).

Clear Queue

await Parse.EventuallyQueue.clear();

Polling

This will call sendQueue when a connection to the server is established. Uses the serverURL used to initialize sdk

Parse.EventuallyQueue.poll();

[codecov]

Codecov Report

Merging #1291 (cf80916) into master (c8270a7) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##            master     #1291    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files           58        59     +1     
  Lines         5650      5788   +138     
  Branches      1273      1299    +26     
==========================================
+ Hits          5650      5788   +138     

Impacted Files	Coverage Δ
src/EventuallyQueue.js	100.00% <100.00%> (ø)
src/Parse.js	100.00% <100.00%> (ø)
src/ParseObject.js	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update c8270a7...cf80916. Read the comment docs.

[mtrezza]

Looks good, should this be flagged as experimental in the changelog like we do with Parse Server sometimes?

[dplewis]

Since we can’t turn it off it’s not experimental.

[dplewis]

I’m using JSON.stringify to save the object in local storage. When I retrieve it’s no longer a class instance or same reference as the stored object. Is their a way to fix this? In a singleInstance environment like the browser objects with the same id have the same state and values. I can’t pass obj1 into destroy since it didn’t get an objectId from save.

[mtrezza]

Not sure I understood this correctly, but Object.create takes the prototype to recreate the instance. Depending on what exactly goes missing, JSON.stringify only stringifies enumerable, own properties, so sometime you may have to write a custom method to serialize/encode and then deserialize/decode an object.

[dplewis]

Stringify calls toJSON() internally. I ran into this issue with the LocalDatastore as well I think.

[dplewis]

I have a few questions that I would like feedback on. @mtrezza @davimacedo

[mtrezza]

Maybe add a chapter about this in the README so people become aware and try this this out? Otherwise LGTM!