First attempt at a parallel promises implementation.

FranticApparatus.xcodeproj/project.pbxproj

@@ -7,6 +7,9 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		E540D8691DDC78B700907960 /* AllPromises.swift in Sources */ = {isa = PBXBuildFile; fileRef = E540D8671DDC78B700907960 /* AllPromises.swift */; };
+		E540D86A1DDC78B700907960 /* AnyPromises.swift in Sources */ = {isa = PBXBuildFile; fileRef = E540D8681DDC78B700907960 /* AnyPromises.swift */; };
+		E540D86C1DDC78BE00907960 /* RacePromises.swift in Sources */ = {isa = PBXBuildFile; fileRef = E540D86B1DDC78BE00907960 /* RacePromises.swift */; };
 		E55CA21719C676DC00E66980 /* FranticApparatus.h in Headers */ = {isa = PBXBuildFile; fileRef = E55CA21619C676DC00E66980 /* FranticApparatus.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		E55CA21D19C676DC00E66980 /* FranticApparatus.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = E55CA21119C676DC00E66980 /* FranticApparatus.framework */; };
 		E57F6CE41D8DDA49006807C4 /* Deferred.swift in Sources */ = {isa = PBXBuildFile; fileRef = E57F6CD81D8DDA49006807C4 /* Deferred.swift */; };
@@ -34,6 +37,9 @@
 /* End PBXContainerItemProxy section */
 
 /* Begin PBXFileReference section */
+		E540D8671DDC78B700907960 /* AllPromises.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = AllPromises.swift; sourceTree = "<group>"; };
+		E540D8681DDC78B700907960 /* AnyPromises.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = AnyPromises.swift; sourceTree = "<group>"; };
+		E540D86B1DDC78BE00907960 /* RacePromises.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = RacePromises.swift; sourceTree = "<group>"; };
 		E55CA21119C676DC00E66980 /* FranticApparatus.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = FranticApparatus.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		E55CA21519C676DC00E66980 /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
 		E55CA21619C676DC00E66980 /* FranticApparatus.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = FranticApparatus.h; sourceTree = "<group>"; };
@@ -132,6 +138,8 @@
 		E57F6CD71D8DDA49006807C4 /* Sources */ = {
 			isa = PBXGroup;
 			children = (
+				E540D8671DDC78B700907960 /* AllPromises.swift */,
+				E540D8681DDC78B700907960 /* AnyPromises.swift */,
 				E57F6CD81D8DDA49006807C4 /* Deferred.swift */,
 				E57F6CD91D8DDA49006807C4 /* Dispatcher.swift */,
 				E57F6CDB1D8DDA49006807C4 /* GCDDispatcher.swift */,
@@ -140,6 +148,7 @@
 				E57F6CDE1D8DDA49006807C4 /* Promise.swift */,
 				E57F6CDF1D8DDA49006807C4 /* PromiseError.swift */,
 				E57F6CE01D8DDA49006807C4 /* PromiseMaker.swift */,
+				E540D86B1DDC78BE00907960 /* RacePromises.swift */,
 				E57F6CE11D8DDA49006807C4 /* Result.swift */,
 				E57F6CE21D8DDA49006807C4 /* State.swift */,
 				E57F6CE31D8DDA49006807C4 /* Thenable.swift */,
@@ -266,7 +275,9 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				E540D86C1DDC78BE00907960 /* RacePromises.swift in Sources */,
 				E57F6CEF1D8DDA49006807C4 /* Thenable.swift in Sources */,
+				E540D86A1DDC78B700907960 /* AnyPromises.swift in Sources */,
 				E57F6CE81D8DDA49006807C4 /* Lock.swift in Sources */,
 				E57F6CEA1D8DDA49006807C4 /* Promise.swift in Sources */,
 				E57F6CEE1D8DDA49006807C4 /* State.swift in Sources */,
@@ -277,6 +288,7 @@
 				E57F6CEB1D8DDA49006807C4 /* PromiseError.swift in Sources */,
 				E57F6CE71D8DDA49006807C4 /* GCDDispatcher.swift in Sources */,
 				E57F6CEC1D8DDA49006807C4 /* PromiseMaker.swift in Sources */,
+				E540D8691DDC78B700907960 /* AllPromises.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

FranticApparatusDemo/FranticApparatusDemo/Info.plist

@@ -51,5 +51,18 @@
 		<string>UIInterfaceOrientationLandscapeLeft</string>
 		<string>UIInterfaceOrientationLandscapeRight</string>
 	</array>
+	<key>NSAppTransportSecurity</key>
+	<dict>
+		<key>NSExceptionDomains</key>
+		<dict>
+			<key>redditmedia.com</key>
+			<dict>
+				<key>NSExceptionAllowsInsecureHTTPLoads</key>
+				<true/>
+				<key>NSIncludesSubdomains</key>
+				<true/>
+			</dict>
+		</dict>
+	</dict>
 </dict>
 </plist>

FranticApparatusDemo/FranticApparatusDemo/RootViewController.swift

@@ -25,6 +25,10 @@
 import UIKit
 import FranticApparatus
 
+enum JSONError : Error {
+    case unexpectedJSON
+}
+
 class RootViewController : UIViewController, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
     var networkAPI: NetworkAPI!
     var collectionView: UICollectionView!
@@ -41,6 +45,8 @@ class RootViewController : UIViewController, UICollectionViewDataSource, UIColle
     var images = [IndexPath : UIImage](minimumCapacity: 8)
     var errors = [IndexPath : Error](minimumCapacity: 8)
     var promises = [IndexPath : Promise<UIImage>](minimumCapacity: 8)
+    var thumbnailsPromise: Promise<[UIImage]>?
+    var thumbnails = [UIImage]()
 
     override func viewDidLoad() {
         super.viewDidLoad()
@@ -65,12 +71,58 @@ class RootViewController : UIViewController, UICollectionViewDataSource, UIColle
         networkAPI = NetworkAPI(dispatcher: networkDispatcher, networkLayer: networkLayer)
     }
 
+    override func viewDidAppear(_ animated: Bool) {
+        super.viewDidAppear(animated)
+
+        if thumbnailsPromise == nil {
+            thumbnailsPromise = PromiseMaker.makeUsing(context: self) { (makePromise) in
+                makePromise { (context) -> Promise<NSDictionary> in
+                    context.networkAPI.requestJSONObjectForURL(URL(string: "https://reddit.com/.json")!)
+                }.whenFulfilledThenPromise { (context, object) -> Promise<[UIImage]> in
+                    let thumbnailURLs = try context.thumbnailsFromJSON(object: object)
+                    let thumbnailPromises = thumbnailURLs.map({ context.networkAPI.requestImageForURL($0) })
+                    return all(thumbnailPromises)
+                }.whenFulfilled { (context, thumbnails) in
+                    context.thumbnails = thumbnails
+                    context.collectionView.reloadData()
+                }.whenRejected { (context, reason) in
+                    NSLog("\(reason)")
+                }.whenComplete { (context) in
+                    context.thumbnailsPromise = nil
+                }
+            }
+        }
+    }
+
+    func thumbnailsFromJSON(object: NSDictionary) throws -> [URL] {
+        guard let data = object["data"] as? NSDictionary else { throw JSONError.unexpectedJSON }
+        guard let children = data["children"] as? NSArray else { throw JSONError.unexpectedJSON }
+        var thumbnailURLs = [URL]()
+        thumbnailURLs.reserveCapacity(children.count)
+
+        for child in children {
+            if let childObject = child as? NSDictionary {
+                if let childData = childObject["data"] as? NSDictionary {
+                    if let thumbnail = childData["thumbnail"] as? NSString {
+                        if thumbnail.hasPrefix("http") {
+                            if let thumbnailURL = URL(string: thumbnail as String) {
+                                thumbnailURLs.append(thumbnailURL)
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        return thumbnailURLs
+    }
+
     func loadImage(at indexPath: IndexPath) {
         let model = models[indexPath.item]
 
         promises[indexPath] = PromiseMaker.makeUsing(context: self) { (makePromise) in
-            makePromise { (context) in
-                return context.networkAPI.requestImageForURL(model.url)
+            makePromise { (context) -> Promise<UIImage> in
+                context.networkAPI.requestImageForURL(model.url)
             }.whenFulfilled { (context, image) in
                 context.images[indexPath] = image
                 context.showImage(at: indexPath)
@@ -125,38 +177,77 @@ class RootViewController : UIViewController, UICollectionViewDataSource, UIColle
         }
     }
 
+    func numberOfSections(in collectionView: UICollectionView) -> Int {
+        if thumbnails.count == 0 {
+            return 1
+        }
+        else {
+            return 2
+        }
+    }
+
     func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
-        return models.count
+        if section == 0 {
+            return models.count
+        }
+        else if section == 1 {
+            return thumbnails.count
+        }
+
+        return 0
     }
 
     func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
-        if let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "imageCell", for: indexPath) as? ImageCell {
-            if let image = images[indexPath] {
-                cell.hideActivity()
-                cell.image = image
+        if indexPath.section == 0 {
+            if let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "imageCell", for: indexPath) as? ImageCell {
+                if let image = images[indexPath] {
+                    cell.hideActivity()
+                    cell.image = image
+                }
+                else if let error = errors[indexPath] {
+                    cell.hideActivity()
+                    cell.error = messageFor(error: error)
+                }
+                else {
+                    cell.showActivity()
+
+                    if promises[indexPath] == nil {
+                        loadImage(at: indexPath)
+                    }
+                }
+
+                return cell
             }
-            else if let error = errors[indexPath] {
+            else {
+                fatalError("No cell to display")
+            }
+        }
+        else if indexPath.section == 1 {
+            if let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "imageCell", for: indexPath) as? ImageCell {
+                let thumbnail = thumbnails[indexPath.item]
                 cell.hideActivity()
-                cell.error = messageFor(error: error)
+                cell.image = thumbnail
+
+                return cell
             }
             else {
-                cell.showActivity()
-
-                if promises[indexPath] == nil {
-                    loadImage(at: indexPath)
-                }
+                fatalError("No cell to display")
             }
-
-            return cell
-        }
-        else {
-            fatalError("No cell to display")
         }
+
+        fatalError("Unexpected indexPath \(indexPath)")
     }
 
     func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
-        let model = models[indexPath.item]
+        if indexPath.section == 0 {
+            let model = models[indexPath.item]
+
+            return CGSize(width: model.width, height: model.height)
+        }
+        else if indexPath.section == 1 {
+            return thumbnails[indexPath.item].size
+        }
 
-        return CGSize(width: model.width, height: model.height)
+        return CGSize.zero
     }
 }