UDSync for Swift

tl;dr: UDSync comes with handy features to support the most common scenarios for offline-first applications.

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Often times we have to build offline first mobile applications or use real time notifications and end up building custom solutions over and over. That guarantees we won't be stuck with outdated libs.

UDSync is not a database.

You will want to use the respective server-side libs to make your life easier: ud-sync-rails

Features

Feature	Description
Synchronization queue (coming soon)	Save records offline and UDSync will add it to the queue and automatically send it to the server once internet comes back.
Synchronize deletions	In an offline-first app, when DeviceA deleted a record, DeviceB needs to know about that when it comes online. UDSync help with that.

Installation

In your Podfile, use

pod 'UDSync'

Usage

Synchronize deletions

Given DeviceA deleted a RecordN while DeviceB was offline, when DeviceB comes online it has to delete RecordN. We keep track of all save/delete operations in the server and expose it via the GET /ud_sync/operations endpoint.

GET /operations

{
  "operations": [{
    "id": "operation-unique-id1",
    "name": "delete",
    "record_id": "record-id1",
    "entity": "user",
    "date": "2015-10-21T10:00:00Z"
  }, {
    "id": "operation-unique-id2",
    "name": "save",
    "record_id": "record-id2",
    "entity": "post",
    "date": "2015-10-21T10:00:00Z"
  }]
}

Based on that, you know what to delete.

In your Swift application, use this piece of code:

// 1. fetch all operations
UDSentinel.sharedInstance.fetchOperations("http://api.myserver.com", accessToken: "") { (operations) in

    // `operations` is an array of UDOperation instances. Each UDOperation
    // responds to (check its test file for more details):
    //
    //   operation.entity() -> the name of the entity that was updated or deleted
    //   operation.operationName() -> either `delete` or `save`
    //   operation.recordId()

    // 2. iterate over each operation
    for operation in operations {
        if operation.operationName() == "delete" {
            if operation.entity() == "Customer" {
                // 3a. delete the record locally

                // Customer class here is your own code
                let id = operation.recordId()
                Customer.find(id).destroy()
            } else if operation.entity() == "Deal" {
                // 3b. delete the record according to the entity name
                //
                // ...
            }
        }
    }
}

License

It's MIT, so do what you wish with it.

Author

Alexandre de Oliveira (@kurko)