Add offline object saving

[mtrezza]

New Feature / Enhancement Checklist

• I am not disclosing a vulnerability.
• I am not just asking a question.
• I have searched through existing issues.

Current Limitation

According to the migration guide, the Parse Swift SDK is missing the feature of offline object saving, which the Parse ObjC supports. This can make it difficult for people to migrate from the Parse ObjC SDK to the Parse Swift SDK. From a forum discussion it seems to require a custom solution and quite some investigation and experimentation to add such a feature.

Offline object saving is currently supported out-of-the-box by all other major Parse SDKs (ObjC, Android, JS).

Feature / Enhancement Description

The Parse Swift SDK should provide offline saving functionality out-of-the-box.

Example Use Case

n/a

Alternatives / Workarounds

Implement a custom solution.

References

• https://docs.parseplatform.org/ios/guide/#saving-objects-offline

[parse-github-assistant]

Thanks for opening this issue!

• 🎉 We are excited about your ideas for improvement!

[hajjD]

Yes, I recently started working on a project that needs to be offline first and realized that this is a gaping hole vs Parse ObjC

[mtrezza]

Did you read through the forum discussion to see whether you can implement a custom solution until this feature is added out-of-the-box to the SDK?

[hajjD]

Unfortunately my time has been rather limited, is there a way I can up the bounty to help out financially?

[vdkdamian]

Unfortunately my time has been rather limited, is there a way I can up the bounty to help out financially?

I have offline usage working for my own project. I could modify it to make it more generic, but I would need to take some days off and I don't know if I find it worth to put in the time and effort for 100$.

Also want to mention that I needed to enable custom objectId's on the server in order for it to work.

Because of this, I don't know if it is suitable for this to publish it.

[mtrezza]

@vdkdamian we could bump the bounty label, how much would you see appropriate for you to add the feature?

[vdkdamian]

@vdkdamian we could bump the bounty label, how much would you see appropriate for you to add the feature?

Difficult question, I would need to see how much work it would take. I've done it using a observable object but I would need to change that in a more general way.

I also think I can drop the fact that custom object id's are required because I only use that for objects that are created locally to be saved when offline.

This would mean that existing objects in the database can be used offline with no problem.

[mtrezza]

Sounds good! So let me know when you get to an estimate, you can also reach me via Slack to discuss in more detail

[vdkdamian]

Sounds good! So let me know when you get to an estimate, you can also reach me via Slack to discuss in more detail

How do I reach you on Slack?

[hajjD]

I am willing to contribute $250 towards the bounty I just need to know how.

[vdkdamian]

I'm still working on it. If finished I'll see what's willing to give as reward.
But definitely working on it now.
Will take some time tho since I have a full-time job and some side projects.

[mtrezza]

@hajjD If you would like to donate to our open collective, we'll raise the bounty for this issue here by the amount that you donate. Whoever provides this feature then gets the bounty, or if multiple people work on this feature, they can easily split up the bounty among them, according to the Parse Bounty Program.

[hajjD]

I contributed $300 via my company, please increase the bounty as such.
transaction_parse-server_2022-12-18_8151efca-4cea-4e76-9080-de4326cf782f.pdf

[mtrezza]

@hajjD Thanks for your contribution! I increased the bounty amount as requested.

[vdkdamian]

@hajjD Could you test this branch?

[hajjD]

Will do, thank you!

[hajjD]

I finally had sometime for in depth testing. There appears to be two major issues:

1. While offline if I create any data it will be lost if I close the app before reconnecting.
2. For the life of me I cant get offline fetching to work. Ill try again tomorrow, as I feel I am missing something.

Another potential issue is when saving etc it will error out if offline, when ideally it should still count as a save if it gets locally stored. This will prevent a bunch of extra boilerplate code to check if online or not.

All in all we are almost there, thank you to everyone involved.

[vdkdamian]

1. While offline if I create any data it will be lost if I close the app before reconnecting.

First of all, did you enable custom objectId? (Also make sure that you set an objectId on initialize of your ParseObject)
Also make sure you set offlinePolicy to .create.

2. For the life of me I cant get offline fetching to work. Ill try again tomorrow, as I feel I am missing something.

Do I understand it correctly that nothing is working?

Another potential issue is when saving etc it will error out if offline, when ideally it should still count as a save if it gets locally stored. This will prevent a bunch of extra boilerplate code to check if online or not.

That's true. I'll check it and see why it's throwing the issue if not connected to the internet.

All in all we are almost there, thank you to everyone involved.

Glad I can help.
If you have some code you can show me, it would be helpful for me to see how you set everything up.
It might be possible I forgot something in the Playground example.
I'm also wondering if you are calling fetchLocal on your ParseObject.
Since this will manage fetching.
I'm pretty sure I forgot to mention this in the Playground examples.
I'll check it out when I have some time.

[hajjD]

Do I understand it correctly that nothing is working?

No, so right now if I save an object and reconnect to the internet it will sync it up as long as the app doesn't close.

I'm also wondering if you are calling fetchLocal on your ParseObject.

I am not, ill get back to you on this as today I also have extra time

[hajjD]

I attempted to use fetchLocal (I could be way off here) as such

Here is the struct

struct TimelineEntry: ParseObject {
    
    // Required for Parse (Protocol)
    var originalData: Data?
    var objectId: String? = UUID().uuidString
    var createdAt: Date?
    var updatedAt: Date?
    var ACL: ParseSwift.ParseACL?
    
    // Our own custom variables
    var date: Date?
    var iconName: String?
    var title: String?
    var subtitle: String?
    var additionalDetails: String?
}

Then saving the data

var newTimelineEntry = TimelineEntry()
newTimeLineEntry.title = "test"
try await newTimelineEntry.save()

Then loading the data

let test = try await TimelineEntry.fetchLocalStore(TimelineEntry.self)
print(test)

Unfortunately it is returning nil when trying to fetch via localStore

[hajjD]

1. While offline if I create any data it will be lost if I close the app before reconnecting.

First of all, did you enable custom objectId? (Also make sure that you set an objectId on initialize of your ParseObject) Also make sure you set offlinePolicy to .create.

Forgot to answer this, yes my config has the following:

offlinePolicy: .create,
                                        requiringCustomObjectIds: true) 

[vdkdamian]

Then saving the data

var newTimelineEntry = TimelineEntry()
newTimeLineEntry.title = "test"
try await newTimelineEntry.save()

This is fine.

Then loading the data

let test = try await TimelineEntry.fetchLocalStore(TimelineEntry.self)
print(test)

Unfortunately it is returning nil when trying to fetch via localStore

I need to point out some things. Getting your objects should still be the same function as you always did.
You will need to make your query and then use .find() to get your object.
I made sure this wouldn't change.

Only thing you need to set is ".useLocalStore()".
Here is an example from the Playground:

let afterDate = Date().addingTimeInterval(-300)
var query = GameScore.query("points" > 50,
                            "createdAt" > afterDate)
    .useLocalStore()
    .order([.descending("points")])
let results = try await query.find()

let test = try await TimelineEntry.fetchLocalStore(TimelineEntry.self)
print(test)

You have set this up correctly, but for now, you will need to set this on your init() or something. This way you can test if everything is working. This is just a manual way of fetching your local objects. I'll try to add this functionality standard on appLaunch and maybe when internet reconnects.

Also, if you look at the description, it states that this will only return results if your objects on the database was more recent then the local. This way you can choose what you do with it.
Generally you won't need the result since it handles it for you.

[kodyholman]

How's this issue coming? Can I help?

[vdkdamian]

How's this issue coming? Can I help?

I was waiting for his answer, but you could help by testing and providing me some feedback.

[gregyoung14]

@vdkdamian I would be happy to help you test this, and help support finishing this feature if needed. @mtrezza Also happy to contribute to the Bounty. Where can I slack you?

[mtrezza]

Hey @gregyoung14 you can join our Slack at https://chat.parseplatform.org. Maybe you could also take a look at @vdkdamian's previous comment, test this PR and provide feedback, to get the PR rolling.