SwiftUI Property Delegates.swift

/// `ObjectBinding` used as a way to create a `Binding` from a `BindableObject`. In this case the ViewModel
/// complies with `BindableObject` which is then translated into a `Binding` which is what `Toggle` is expecting
/// NOTE: Since it's a `DynamicViewProperty`, after its value is changed, the body will be updated.
class ViewModel: BindableObject {

   let didChange = PassthroughSubject<ViewModel, Never>()

   var isEnabled = false {
       didSet {
           didChange.send(self)
       }
   }
}

struct ObjectBinding_ExampleView : View {

   @ObjectBinding(initialValue: ViewModel()) var viewModel: ViewModel

   var body: some View {
       Toggle(isOn: $viewModel.isEnabled) {
           Text("The value is " + "\(viewModel.isEnabled)")
       }
   }
}

/// ==================================

/// `State` used as a quick way to store a mutable, bindable entity. 
/// NOTE: Since it's a `DynamicViewProperty`, after its value is changed, the body will be updated.
struct State_ExampleView : View {

   @State var value: Bool

   var body: some View {
       Toggle(isOn: $value) {
           Text("The value is " + "\($value)")
       }
   }
}

/// ==================================

/// `Environment` used to get values from `EnvironmentValues`. These range from `Calendar` to `ColorScheme`, `Fonts`, `Locale`
/// and others
struct ContentView : View {

    @Environment(\.isEnabled) var enabled: Bool

    var body: some View {
        Text("The value is " + "\(enabled)")
    }
}

/// ==================================

/// `@EnvironmentObject` acts like a DI Container for Binds. You can register anything that conforms to `Bindable` via
///  `.environmentObject` and use `@EnvironmentObject` to read that value from the container.
/// NOTE: Since it's a `DynamicViewProperty`, after its value is changed, the body will be updated.
class ViewModel: BindableObject {

    let didChange = PassthroughSubject<ViewModel, Never>()

    var isEnabled = false {
        didSet {
            didChange.send(self)
        }
    }
}

struct ContentView : View {

    @EnvironmentObject var viewModel: ViewModel

    var body: some View {
        Toggle(isOn: $viewModel.isEnabled) {
            Text("The value is " + "\(viewModel.isEnabled)")
        }
    }
}
/// You create the ContentView and associate the type
/// The `var viewModel` is set automatically for you. 
let view = ContentView().environmentObject(ViewModel())

/// ==================================

/// `Binding` is a wraper for a setter and a getter. It's the `@ObjectBinding` in this case that kicks the view
///  renderization.
class ViewModel: BindableObject {
    
    let didChange = PassthroughSubject<ViewModel, Never>()
    
    var textInput = "" {
        didSet {
            didChange.send(self)
        }
    }
}

struct ContentView : View {
    
    @ObjectBinding var viewModel: ViewModel
    
    init(viewModel: ViewModel) {
        self.viewModel =  viewModel
    }
    
    var body: some View {
        List {
            Text("email")
            TextField(viewModel[\.textInput])
        }
    }
}