SwiftUI’s design takes advantage of equality to decide if things should be updated. Measurement (backed by NSMeasurement) has something interesting in its Equatable implementation: This means that 0kg is equal to 0g despite their unit being different. This makes sense for comparing weights but not for using it to decide Read more
Reposted from: https://forums.swift.org/t/how-to-use-observation-to-actually-observe-changes-to-a-property/67591/18 I thought I’d share an example of how I am currently using it. I wanted to make an object that maintains a sorted order of the main model’s objects. I used withObservationTracking to update if either the sort order local to this object is changed or if the particular Read more
I came across this StackOverflow question How do I access the SwiftData container from outside of SwiftUI? but it turns out they needed to use the container inside an AppIntent. I knew the way to inject objects into AppIntents is via the AppDependencyManager but I’d never actually tried it with Read more
Health warning: In general I would not recommend this approach. View data should be @State simple values or custom structs with mutating func for testable logic, passed down as let for read only, computed vars for transforming, or @Binding var for read/write. @Observable is designed for data models, e.g. loading Read more
If you attempt to init another instance of CLMonitor with the same name it crashes with: Since I wanted to use the same monitor from different tasks I needed to turn it into a singleton and came up with this: This allows this kind of thing to work without crashing: Read more
Following on from my previous post on this topic I found a forum post with someone struggling to build a calculator using @Observable and thought maybe my technique of wrapping withObservationTracking in AsyncStream might help and came up with the code below which appears to work. Obviously this code comes Read more
I needed to create an AsyncStream to monitor changes to an @Observable model class’s var and by using withCheckedContinuation and AsyncStream‘s unfolding init I came up with this: The challenge here is withObservationTracking only watches for a single change but we can wrap that in withCheckedContinuation which also is designed Read more
I noticed a snag when using NavigationLink(value:label:) and .navigationDestination(for:destination:) with the new @Observable vs the old Combine ObservableObject (which “just worked™️”). There are 2 compilation errors: Fortunately it is relatively simple to add Hashable conformance to an @Observable class by implementing a static func == and a func hash that Read more
In SwiftIUI, when requiring the reference semantics of a class and wanting to upgrade from Combine’s ObservableObject and @StateObject to the new @Observable it requires a bit more work to get the life-cycle correct. The reason for this is we have to store the object in @State which is designed Read more
Today I successfully cloned my M1 MacBook Air to a new M3 MacBook Pro, it took some effort so thought I would share the steps here. Before I begin, the reason I prefer to clone rather than use Migration Assistant is I have many command line tools installed all over Read more