Equivalent of Androids DiffUtil for Swift / iOS or other effective implementation

Question

In my app I have to load some data from a web service. Then I have to sort the data by properties of models of a collection property of the model and then update my collectio view with the new data.

Unfortunately I have no clue how I can know which cell moved to which new position. On Android, I used DiffUtil in the past but I'm not aware of a Swift equivalent to animate the changes in my collection view.

Heres the data model I use. For the this example, I omit all the other fields and use protocols to make it clearer (at least I hope this makes it clearer):

protocol Alert {
  var date: Date
  var statusType: StatusType
}

protocol Status {
  var statusType: StatusType
  var level: Level
}

protocol Device {
  var states: [Status] //Contains never more than 1 Status of each StatusType so its basically a set
  var alertsByStatusType: [StatusType: [Alert]]
}

enum StatusType {
  case someStatus, someOtherStatus
}

enum Level {
  case low, medium, high
}

The web service returns me a device which contains a collection of Status and a collection of Alert.

//Web service model kind of sucks
protocl WebServiceDevice {
  var states: [Status]
  var alerts: [Alert]
}

In the device constructor, I do some manually sorting and mapping to build the alertsByStatusType dictionary. I also sort the Status collection by the Status.level so that first, all "high" level states come, then the "medium" level and finally the "low" level states.

Inside the same level, I then have to sort by the Alerts.date so when two Status have the same Level, the one with the more recent Alert comes first.

I know, this data model I get from the web service is terrible to begin with and I begged for a proper model where the alerts are inside their corresponding states and the states are properly sorted but hey, thats life.

Now when I display all states in a tableview, let's say a Status with level == low gets and alert, then the level will change and after updating my data from the web service and sorting everything, it will be further to the beginning in the Device.states collection. How can I know from which indexPath I have to move the cell to which new indexPath?

I hope you understand what I mean and what the problem is. Basically I have to find out which Status has a different Level and from where to where it has moved in the data source of my table view so I can animate the changes instead just call reload() on the table view.

Answer 1

I'm not sure why but the answer I selected as correct for this question has vanished so I thought I'd answer it myself. I was pointed to a library which can do exactly that and by the time of writing, I found more libraries.

They probably all have their ups and downs and the one I use now is the Dwifft Library (https://github.com/jflinter/Dwifft)

Other interesting diff libraries can be found here: https://awesome-repos.ecp.plus/ios.html under the Data Structures / Algorithms section