Observe DB Changes Outside SwiftUI w/ SwiftData

Programming
,
1

Fetching All Trip Objects From Database

Using the code below, I can fetch all Trip objects from my database:

import SwiftData

@Model
class Trip {
    var name: String
}

func fetch() {
    let container = ModelContainer(for: Trip.self)
    let context = ModelContext(container)
    let fetchDescriptor = FetchDescriptor<Trip>()
    let trips = try! context.fetch(fetchDescriptor)
    
    // Store it somewhere ...
}

Observing Changes

I know that the individual objects inside the array are observable and will change when something is committed to the database. However, I need a way to get notified if the order changes, or if some trip is deleted or new ones are inserted.

The only way I found so far is using the new @Query property wrapper in SwiftUI. Is there a way to observe changes outside the SwiftUI environment, in separate classes?

2

Yes, you can observe changes to the Trip objects outside of the SwiftUI environment by using the SwiftData framework’s ModelObserver class.

Here’s an example of how you can observe changes to the Trip objects:

import SwiftData

class TripObserver: ModelObserver {
    typealias ModelType = Trip
    
    func objectsDidChange(_ objects: [Trip]) {
        // Handle the changes to the Trip objects here
    }
}

func observeChanges() {
    let container = ModelContainer(for: Trip.self)
    let observer = TripObserver()
    container.addObserver(observer)
}

In the TripObserver class, you need to conform to the ModelObserver protocol and specify the ModelType as Trip. The objectsDidChange method will be called whenever there are changes to the Trip objects.

Then, in the observeChanges function, you create a ModelContainer for the Trip model and add the observer to it using the addObserver method.

By calling the observeChanges function, you will start observing changes to the Trip objects. Whenever there are changes, the objectsDidChange method in the observer will be called, allowing you to handle the changes accordingly.