introducing a lastState property and completion handlers when the current state changes (fixes #5)

Author: aschuch

Example/ViewController.swift

@@ -30,21 +30,28 @@ class ViewController: StatefulViewController {
 	}
 
 	override func viewWillAppear(animated: Bool) {
+        refresh()
+        
 		super.viewWillAppear(animated)
-
-		refresh()
 	}
 
 	func refresh() {
-		if (currentState == .Loading) { return }
-		startLoading()
+		if (lastState == .Loading) { return }
+        
+        startLoading(completion: {
+            println("completaion startLoading -> loadingState: \(self.currentState.rawValue)")
+        })
+        println("startLoading -> loadingState: \(self.lastState.rawValue)")
 
         // Fake network call
-		dispatch_after(dispatch_time(DISPATCH_TIME_NOW, Int64(1.5 * Double(NSEC_PER_SEC))), dispatch_get_main_queue()) {
+		dispatch_after(dispatch_time(DISPATCH_TIME_NOW, Int64(3 * Double(NSEC_PER_SEC))), dispatch_get_main_queue()) {
 			// Success
 			self.dataArray = ["Merlot", "Sauvignon Blanc", "Blaufränkisch", "Pinot Nior"]
 			self.tableView.reloadData()
-			self.endLoading(error: nil)
+            self.endLoading(error: nil, completion: {
+                println("completion endLoading -> loadingState: \(self.currentState.rawValue)")
+            })
+            println("endLoading -> loadingState: \(self.lastState.rawValue)")
 			self.refreshControl.endRefreshing()
 
 			// Error

StatefulViewController/StatefulViewController.swift

@@ -43,11 +43,17 @@ public class StatefulViewController: UIViewController {
 	/// All states other than `Content` imply that there is a placeholder view shown.
 	public var currentState: StatefulViewControllerState {
 		switch stateMachine.currentState {
-			case .None: return .Content
-			case .View(let viewKey): return StatefulViewControllerState(rawValue: viewKey)!
+        case .None: return .Content
+		case .View(let viewKey): return StatefulViewControllerState(rawValue: viewKey)!
 		}
 	}
 
+    public var lastState: StatefulViewControllerState {
+        switch stateMachine.currentState {
+        case .None: return .Content
+        case .View(let viewKey): return StatefulViewControllerState(rawValue: viewKey)!
+        }
+    }
 
 	// MARK: Views
 
@@ -71,8 +77,11 @@ public class StatefulViewController: UIViewController {
 
 	override public func viewWillAppear(animated: Bool) {
 		super.viewWillAppear(animated)
-
-		transitionViewStates(animated: false)
+        
+        // Make sure to stay in the correct state when transitioning
+        let isLoading = (currentState == .Loading)
+        let error: NSError? = (currentState == .Error) ? NSError() : nil
+		transitionViewStates(loading: isLoading, error: error, animated: false)
 	}
 
 
@@ -83,8 +92,8 @@ public class StatefulViewController: UIViewController {
 	///
 	/// :param: animated	true if the switch to the placeholder view should be animated, false otherwise
 	///
-	public func startLoading(animated: Bool = false) {
-		transitionViewStates(loading: true, animated: animated)
+    public func startLoading(animated: Bool = false, completion: (() -> ())? = nil) {
+        transitionViewStates(loading: true, animated: animated, completion: completion)
 	}
 
 	/// Ends the controller's loading state.
@@ -94,8 +103,8 @@ public class StatefulViewController: UIViewController {
 	/// :param: animated	true if the switch to the placeholder view should be animated, false otherwise
 	/// :param: error		An error that might have occured whilst loading
 	///
-	public func endLoading(animated: Bool = true, error: NSError? = nil) {
-		transitionViewStates(loading: false, animated: animated, error: error)
+	public func endLoading(animated: Bool = true, error: NSError? = nil, completion: (() -> ())? = nil) {
+		transitionViewStates(loading: false, animated: animated, error: error, completion: completion)
 	}
 
 
@@ -108,29 +117,27 @@ public class StatefulViewController: UIViewController {
 	/// :param: error		An error that might have occured whilst loading
 	/// :param: animated	true if the switch to the placeholder view should be animated, false otherwise
 	///
-	public func transitionViewStates(loading: Bool = false, error: NSError? = nil, animated: Bool = true) {
-		dispatch_async(dispatch_get_main_queue()) {
-            let hasContent = (self as? StatefulViewControllerDelegate)?.hasContent() ?? true
-            
-			// Update view for content (i.e. hide all placeholder views)
-			if hasContent {
-				if let e = error {
-					// show unobstrusive error
-					(self as? StatefulViewControllerDelegate)?.handleErrorWhenContentAvailable?(e)
-				}
-				self.stateMachine.transitionToState(.None, animated: animated)
-				return
-			}
-			
-			// Update view for placeholder
-			var newState: StatefulViewControllerState = .Empty
-			if loading {
-				newState = .Loading
-			} else if let e = error {
-				newState = .Error
-			}
-			self.stateMachine.transitionToState(.View(newState.rawValue), animated: animated)
-		}
+    public func transitionViewStates(loading: Bool = false, error: NSError? = nil, animated: Bool = true, completion: (() -> ())? = nil) {
+        let hasContent = (self as? StatefulViewControllerDelegate)?.hasContent() ?? true
+        
+        // Update view for content (i.e. hide all placeholder views)
+        if hasContent {
+            if let e = error {
+                // show unobstrusive error
+                (self as? StatefulViewControllerDelegate)?.handleErrorWhenContentAvailable?(e)
+            }
+            self.stateMachine.transitionToState(.None, animated: animated, completion: completion)
+            return
+        }
+        
+        // Update view for placeholder
+        var newState: StatefulViewControllerState = .Empty
+        if loading {
+            newState = .Loading
+        } else if let e = error {
+            newState = .Error
+        }
+        self.stateMachine.transitionToState(.View(newState.rawValue), animated: animated, completion: completion)
 	}
 
 

StatefulViewController/ViewStateMachine.swift

@@ -41,7 +41,10 @@ public class ViewStateMachine {
     /// The current display state of views
 	public private(set) var currentState: ViewStateMachineState = .None
 
+    /// The last state that was enqueued
+    public private(set) var lastState: ViewStateMachineState = .None
 
+    
 	// MARK: Init
 
 	///  Designated initializer.
@@ -109,6 +112,8 @@ public class ViewStateMachine {
 	/// :param: campletion	called when all animations are finished and the view has been updated
 	///
 	public func transitionToState(state: ViewStateMachineState, animated: Bool = true, completion: (() -> ())? = nil) {
+        lastState = state
+        
 		dispatch_async(queue) {
 			if state == self.currentState {
 				return