onAppear vs .task — when to use which?

Middle PRO

The gist

• .onAppear { } — a synchronous callback: the view entered the hierarchy. Paired with .onDisappear. It cancels nothing and knows nothing about async.
• .task { } — starts a Task tied to the view's lifetime: the closure is async, and when the view disappears (or the id changes) the task is cancelled automatically. This is the standard way to load data with async/await.
• .task(id:) { } — restarts when id changes: the previous task is cancelled and a new one starts. Ideal for "reload when the query / selected item changes".