How SwiftUI tracks changes in SwiftData objects
How SwiftUI tracks changes in SwiftData objects 관련
Updated for Xcode 15
SwiftUI and SwiftData are built with tight coordination, which allows SwiftUI to update its views only when your SwiftData object changes a value that actually matters – any property that is actually used by the view will cause an update, but changing other values won't.
Internally this is all powered by Swift's observation system: when SwiftUI renders a view it makes a list of all the properties that are read from Observable objects, then watch those properties – and only those – for changes. When any do change, that view gets re-evaluated and the whole process repeats.
Tips
This whole process works equally well with computed properties – as long as calling a computed property refers to a stored property on your object, SwiftUI will take note that it was accessed when your view was rendered.
Because SwiftData's objects are built on top of the Swift's observation system, all our objects automatically inherit this same power: views that use one of your model objects won't update until a property they directly rely on has changed. So, if your view refers to a user's name, it won't refresh if that's user's age changes – it's a big performance win.
Important
If you have a SwiftUI view that depends on one or more properties from a SwiftData object, changing that property will cause the view to be invalidated and re-rendered even if it's currently positioned off-screen.