How to pass ObservedObject as parameter in SwiftUI

Issue #685

Since we have custom init in ChildView to manually set a State, we need to pass ObservedObject. In the ParentView, use underscore _ to access property wrapper type.

struct ChildView: View {
    @ObservedObject
    var store: Store

    @State
    private var selectedTask: AnyTask

    init(store: ObservedObject<Store>) {
        _selectedTask = State(initialValue: tasks.first!)
        _store = store
    }
}

struct ParentView: View {
    @ObservedObject
    var store: Store

    var body: some View {
        ChildView(store: _store)
    }