Update docs and template for ViewEnvironment

docs/tutorial/building-a-view-controller-from-screen.md

@@ -11,16 +11,20 @@ controller from a view model update.
 struct DemoScreen: Screen {
     let title: String
     let onTap: () -> Void
+
+    func viewControllerDescription(environment: ViewEnvironment) -> ViewControllerDescription {
+        return DemoScreenViewController.description(for: self, environment: environment)
+    }
 }
 
 
 class DemoScreenViewController: ScreenViewController<DemoScreen> {
 
     private let button: UIButton
 
-    required init(screen: DemoScreen) {
+    required init(screen: DemoScreen, environment: ViewEnvironment) {
         button = UIButton()
-        super.init(screen: screen)
+        super.init(screen: screen, environment: environment)
 
         update(screen: screen)
     }
@@ -39,8 +43,8 @@ class DemoScreenViewController: ScreenViewController<DemoScreen> {
         button.frame = view.bounds
     }
 
-    override func screenDidChange(from previousScreen: DemoScreen) {
-        super.screenDidChange(from: previousScreen)
+    override func screenDidChange(from previousScreen: DemoScreen, previousEnvironment: ViewEnvironment) {
+        super.screenDidChange(from: previousScreen, previousEnvironment: previousEnvironment)
         update(screen: screen)
     }
 
@@ -64,5 +68,5 @@ class DemoScreenViewController: ScreenViewController<DemoScreen> {
 1. The button is tapped. When the callback is called, we call the `onTap` closure passed into the
    screen. The workflow will handle this event, update its state, and a new screen will be rendered.
 1. The updated screen is passed to the view controller via the
-   `screenDidChange(from previousScreen:)` method. Again, the view controller updates the title of
-   the button based on what was passed in the screen.
+   `screenDidChange(from previousScreen: previousEnvironment: previousEnvironment:)` method. Again,
+   the view controller updates the title of the button based on what was passed in the screen.

swift/Samples/Tutorial/Tutorial1.md

@@ -44,8 +44,8 @@ struct WelcomeScreen: Screen {
     /// Callback when the login button is tapped.
     var onLoginTapped: () -> Void
 
-    var viewControllerDescription: ViewControllerDescription {
-        return WelcomeViewController.description(for: self)
+    func viewControllerDescription(environment: ViewEnvironment) -> ViewControllerDescription {
+        return WelcomeViewController.description(for: self, environment: environment)
     }
 }
 ```

swift/Samples/Tutorial/Tutorial3.md

@@ -89,8 +89,8 @@ The `Screen` protocol also requires a `viewControllerDescription` property. This
 
 ```swift
 extension TodoEditScreen {
-    var viewControllerDescription: ViewControllerDescription {
-        TodoEditViewController.description(for: self)
+    func viewControllerDescription(environment: ViewEnvironment) -> ViewControllerDescription {
+        TodoEditViewController.description(for: self, environment: environment)
     }
 }
 ```

swift/Tooling/Templates/Screen (View Controller).xctemplate/___FILEBASENAME___Screen.swift

@@ -10,24 +10,24 @@ struct ___VARIABLE_productName___Screen: Screen {
     // It should also contain callbacks for any UI events, for example:
     // var onButtonTapped: () -> Void
 
-    var viewControllerDescription: ViewControllerDescription {
-        return ___VARIABLE_productName___ViewController.description(for: self)
+    func viewControllerDescription(environment: ViewEnvironment) -> ViewControllerDescription {
+        return ___VARIABLE_productName___ViewController.description(for: self, environment: environment)
     }
 }
 
 
 final class ___VARIABLE_productName___ViewController: ScreenViewController<___VARIABLE_productName___Screen> {
 
-    required init(screen: ___VARIABLE_productName___Screen) {
-        super.init(screen: screen)
-        update(with: screen)
+    required init(screen: ___VARIABLE_productName___Screen, environment: ViewEnvironment) {
+        super.init(screen: screen, environment: environment)
+        update(with: screen, environment: environment)
     }
 
-    override func screenDidChange(from previousScreen: ___VARIABLE_productName___Screen) {
-        update(with: screen)
+    override func screenDidChange(from previousScreen: ___VARIABLE_productName___Screen, previousEnvironment: ViewEnvironment) {
+        update(with: screen, environment: environment)
     }
 
-    private func update(with screen: ___VARIABLE_productName___Screen) {
+    private func update(with screen: ___VARIABLE_productName___Screen, environment: ViewEnvironment) {
         /// Update UI
     }
 

swift/WorkflowUI/Sources/Screen/ScreenViewController.swift

@@ -25,13 +25,13 @@ import UIKit
 /// Using this base class, a screen can be implemented as:
 /// ```
 /// struct MyScreen: Screen {
-///     var viewControllerDescription: ViewControllerDescription {
+///     func viewControllerDescription(environment: ViewEnvironment) -> ViewControllerDescription {
 ///         return MyScreenViewController.description(for: self)
 ///     }
 /// }
 ///
 /// private class MyScreenViewController: ScreenViewController<MyScreen> {
-///     override func screenDidChange(from previousScreen: MyScreen) {
+///     override func screenDidChange(from previousScreen: MyScreen, previousEnvironment: ViewEnvironment) {
 ///         // … update views as necessary
 ///     }
 /// }