[WIP] @ResourceBacked property wrapper

Cartfile

@@ -0,0 +1 @@
+

Examples/GithubBrowser/GithubBrowser.xcodeproj/xcshareddata/xcschemes/GithubBrowser.xcscheme

@@ -0,0 +1,78 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Scheme
+   LastUpgradeVersion = "1140"
+   version = "1.3">
+   <BuildAction
+      parallelizeBuildables = "YES"
+      buildImplicitDependencies = "YES">
+      <BuildActionEntries>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "YES"
+            buildForProfiling = "YES"
+            buildForArchiving = "YES"
+            buildForAnalyzing = "YES">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "DA7462381B4C768B00406D67"
+               BuildableName = "GithubBrowser.app"
+               BlueprintName = "GithubBrowser"
+               ReferencedContainer = "container:GithubBrowser.xcodeproj">
+            </BuildableReference>
+         </BuildActionEntry>
+      </BuildActionEntries>
+   </BuildAction>
+   <TestAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      shouldUseLaunchSchemeArgsEnv = "YES">
+      <Testables>
+      </Testables>
+   </TestAction>
+   <LaunchAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      launchStyle = "0"
+      useCustomWorkingDirectory = "NO"
+      ignoresPersistentStateOnLaunch = "NO"
+      debugDocumentVersioning = "YES"
+      debugServiceExtension = "internal"
+      allowLocationSimulation = "YES">
+      <BuildableProductRunnable
+         runnableDebuggingMode = "0">
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "DA7462381B4C768B00406D67"
+            BuildableName = "GithubBrowser.app"
+            BlueprintName = "GithubBrowser"
+            ReferencedContainer = "container:GithubBrowser.xcodeproj">
+         </BuildableReference>
+      </BuildableProductRunnable>
+   </LaunchAction>
+   <ProfileAction
+      buildConfiguration = "Release"
+      shouldUseLaunchSchemeArgsEnv = "YES"
+      savedToolIdentifier = ""
+      useCustomWorkingDirectory = "NO"
+      debugDocumentVersioning = "YES">
+      <BuildableProductRunnable
+         runnableDebuggingMode = "0">
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "DA7462381B4C768B00406D67"
+            BuildableName = "GithubBrowser.app"
+            BlueprintName = "GithubBrowser"
+            ReferencedContainer = "container:GithubBrowser.xcodeproj">
+         </BuildableReference>
+      </BuildableProductRunnable>
+   </ProfileAction>
+   <AnalyzeAction
+      buildConfiguration = "Debug">
+   </AnalyzeAction>
+   <ArchiveAction
+      buildConfiguration = "Release"
+      revealArchiveInOrganizer = "YES">
+   </ArchiveAction>
+</Scheme>

Examples/GithubBrowser/Podfile

@@ -4,4 +4,5 @@ target 'GithubBrowser' do
   use_frameworks!
 
   pod 'Siesta/UI', path: '../..'
+  pod 'Siesta/Tools', path: '../..'
 end

Examples/GithubBrowser/Podfile.lock

@@ -1,18 +1,21 @@
 PODS:
   - Siesta/Core (1.5.0)
+  - Siesta/Tools (1.5.0):
+    - Siesta/Core
   - Siesta/UI (1.5.0):
     - Siesta/Core
 
 DEPENDENCIES:
+  - Siesta/Tools (from `../..`)
   - Siesta/UI (from `../..`)
 
 EXTERNAL SOURCES:
   Siesta:
     :path: "../.."
 
 SPEC CHECKSUMS:
-  Siesta: 407b99ae05344d2de33d98e9e239551086daee6a
+  Siesta: 31a12f6f9905bd144cfadaa861a0cdd55c2faa17
 
-PODFILE CHECKSUM: 974001388daa9ecbfa915ea0bc4093a33242099c
+PODFILE CHECKSUM: 96de1def0845d136c0ee748e2599bcfc49e6b814
 
 COCOAPODS: 1.9.1

Examples/GithubBrowser/Source/API/GithubAPI.swift

@@ -16,7 +16,7 @@ class _GitHubAPI {
     fileprivate init() {
         #if DEBUG
             // Bare-bones logging of which network calls Siesta makes:
-            SiestaLog.Category.enabled = [.network]
+            SiestaLog.Category.enabled = [.network, .cache]
 
             // For more info about how Siesta decides whether to make a network call,
             // and which state updates it broadcasts to the app:
@@ -43,13 +43,48 @@ class _GitHubAPI {
 
             $0.pipeline[.cleanup].add(
               GitHubErrorMessageExtractor(jsonDecoder: jsonDecoder))
+
+            // Cache API results for fast launch & offline access:
+
+            $0.pipeline[.rawData].cacheUsing {
+                try FileCache<Data>(
+                    poolName: "api.github.com",
+                    dataIsolation: .perUser(identifiedBy: self.username))  // Show each user their own data
+            }
+
+            // Using the closure form of cacheUsing above signals that if we encounter an error trying create a cache
+            // directory or generate a cache isolation key from the username, we should simply proceed silently without
+            // having a persistent cache.
+
+            // Note that the dataIsolation uses only username. This means that users will not _see_ other users’ data;
+            // however, it does not _secure_ one user’s data from another. A user with permission to see the cache
+            // directory could in principle see all the cached data.
+            //
+            // To fully secure one user’s data from another, the application would need to generate some long-lived
+            // secret that is unique to each user. A password can work, though it will essentially empty the user’s
+            // cache if the password changes. The server could also send some kind of high-entropy per-user token in
+            // the authentication response.
         }
 
+        RemoteImageView.defaultImageService.configure {
+            // We can cache images offline too:
+
+            $0.pipeline[.rawData].cacheUsing {
+                try FileCache<Data>(
+                    poolName: "images",
+                    dataIsolation: .sharedByAllUsers)  // images aren't secret, so no need to isolate them
+            }
+        }
+
+
         // –––––– Resource-specific configuration ––––––
 
         service.configure("/search/**") {
             // Refresh search results after 10 seconds (Siesta default is 30)
             $0.expirationTime = 10
+
+            // Don't cache search results between runs, so we don't see stale results on launch
+            $0.pipeline.removeAllCaches()
         }
 
         // –––––– Auth configuration ––––––
@@ -115,19 +150,23 @@ class _GitHubAPI {
     // MARK: - Authentication
 
     func logIn(username: String, password: String) {
-        if let auth = "\(username):\(password)".data(using: String.Encoding.utf8) {
+        self.username = username
+        if let auth = "\(username):\(password)".data(using: .utf8) {
             basicAuthHeader = "Basic \(auth.base64EncodedString())"
         }
     }
 
     func logOut() {
+        username = nil
         basicAuthHeader = nil
     }
 
     var isAuthenticated: Bool {
         return basicAuthHeader != nil
     }
 
+    private var username: String?
+
     private var basicAuthHeader: String? {
         didSet {
             // These two calls are almost always necessary when you have changing auth for your API:

Examples/GithubBrowser/Source/UI/RepositoryListViewController.swift

@@ -5,30 +5,13 @@ class RepositoryListViewController: UITableViewController, ResourceObserver {
 
     // MARK: Interesting Siesta stuff
 
-    var repositoriesResource: Resource? {
-        didSet {
-            oldValue?.removeObservers(ownedBy: self)
-
-            repositoriesResource?
-                .addObserver(self)
-                .addObserver(statusOverlay, owner: self)
-                .loadIfNeeded()
-        }
-    }
-
-    var repositories: [Repository] = [] {
-        didSet {
-            tableView.reloadData()
-        }
-    }
+    @ResourceBacked(default: [])
+    var repositories: [Repository]
 
     var statusOverlay = ResourceStatusOverlay()
 
     func resourceChanged(_ resource: Resource, event: ResourceEvent) {
-        // Siesta’s typedContent() infers from the type of the repositories property that
-        // repositoriesResource should hold content of type [Repository].
-
-        repositories = repositoriesResource?.typedContent() ?? []
+        tableView.reloadData()
     }
 
     // MARK: Standard table view stuff
@@ -37,7 +20,12 @@ class RepositoryListViewController: UITableViewController, ResourceObserver {
         super.viewDidLoad()
 
         view.backgroundColor = SiestaTheme.darkColor
+
         statusOverlay.embed(in: self)
+        statusOverlay.displayPriority = [.anyData, .loading, .error]
+
+        $repositories.addObserver(self)
+        $repositories.addObserver(statusOverlay)
     }
 
     override func viewDidLayoutSubviews() {
@@ -65,8 +53,8 @@ class RepositoryListViewController: UITableViewController, ResourceObserver {
             if let repositoryVC = segue.destination as? RepositoryViewController,
                let cell = sender as? RepositoryTableViewCell {
 
-                repositoryVC.repositoryResource =
-                    repositoriesResource?.optionalRelative(
+                repositoryVC.$repository.resource =
+                    $repositories.resource?.optionalRelative(
                         cell.repository?.url)
             }
         }

Examples/GithubBrowser/Source/UI/RepositoryViewController.swift

@@ -25,48 +25,25 @@ class RepositoryViewController: UIViewController, ResourceObserver {
 
     // MARK: Resources
 
-    var repositoryResource: Resource? {
-        didSet {
-            updateObservation(from: oldValue, to: repositoryResource)
-        }
-    }
+    @ResourceBacked(default: nil)
+    var repository: Repository?
 
-    var starredResource: Resource? {
-        didSet {
-            updateObservation(from: oldValue, to: starredResource)
-        }
-    }
+    @ResourceBacked(default: false)
+    var isStarred: Bool
 
-    var languagesResource: Resource? {
-        didSet {
-            updateObservation(from: oldValue, to: languagesResource)
-        }
-    }
+    @ResourceBacked(default: [:])
+    var languages: [String:Int]
 
-    var contributorsResource: Resource? {
-        didSet {
-            updateObservation(from: oldValue, to: contributorsResource)
-        }
-    }
+    @ResourceBacked(default: [])
+    var contributors: [User]
 
     private func updateObservation(from oldResource: Resource?, to newResource: Resource?) {
         guard oldResource != newResource else { return }
 
-        oldResource?.removeObservers(ownedBy: self)
-        newResource?
-            .addObserver(self)
-            .addObserver(statusOverlay, owner: self)
-            .loadIfNeeded()
-    }
-
-    // MARK: Content conveniences
-
-    var repository: Repository? {
-        return repositoryResource?.typedContent()
-    }
-
-    var isStarred: Bool {
-        return starredResource?.typedContent() ?? false
+        for resourceBox in [$repository, $isStarred, $languages, $contributors] as [AnyResourceBacked] {
+            resourceBox.addObserver(self)
+            resourceBox.addObserver(statusOverlay)
+        }
     }
 
     // MARK: Display
@@ -75,6 +52,7 @@ class RepositoryViewController: UIViewController, ResourceObserver {
         super.viewDidLoad()
 
         view.backgroundColor = SiestaTheme.darkColor
+
         statusOverlay.embed(in: self)
         statusOverlay.displayPriority = [.anyData, .loading, .error]  // Prioritize partial data over loading indicator
 
@@ -117,37 +95,30 @@ class RepositoryViewController: UIViewController, ResourceObserver {
         descriptionLabel?.text = repository?.description
         homepageButton?.setTitle(repository?.homepage, for: .normal)
 
-        if let contributors: [User] = contributorsResource?.typedContent() {
-            contributorsLabel?.text = contributors
-                .map { $0.login }
-                .joined(separator: "\n")
-        } else {
-            contributorsLabel?.text = "–"
-        }
+        contributorsLabel?.text = contributors
+            .map { $0.login }
+            .joined(separator: "\n")
 
-        if let languages: [String:Int] = languagesResource?.typedContent() {
-            languagesLabel?.text = languages.keys.joined(separator: " • ")
-        } else {
-            languagesLabel?.text = "–"
-        }
+        languagesLabel?.text = languages.keys.joined(separator: " • ")
     }
 
     func showStarred() {
         if let repository = repository {
-            starredResource = GitHubAPI.currentUserStarred(repository)
+            $isStarred.resource = GitHubAPI.currentUserStarred(repository)
         } else {
-            starredResource = nil
+            $isStarred.resource = nil
         }
 
-        contributorsResource = repositoryResource?.optionalRelative(
+        $contributors.resource = $repository.resource?.optionalRelative(
             repository?.contributorsURL)
-        languagesResource = repositoryResource?.optionalRelative(
+        $languages.resource = $repository.resource?.optionalRelative(
             repository?.languagesURL)
 
         starCountLabel?.text = repository?.starCount?.description
         starIcon?.text = isStarred ? "★" : "☆"
         starButton?.setTitle(isStarred ? "Unstar" : "Star", for: .normal)
-        starButton?.isEnabled = (repository != nil)
+        starButton?.isEnabled = ($isStarred.resource != nil)
+        starButton?.alpha = ($isStarred.resource != nil) ? 1 : 0.3
     }
 
     // MARK: Actions

Examples/GithubBrowser/Source/UI/UserViewController.swift

@@ -52,6 +52,8 @@ class UserViewController: UIViewController, UISearchBarDelegate, ResourceObserve
         view.backgroundColor = SiestaTheme.darkColor
 
         statusOverlay.embed(in: self)
+        statusOverlay.displayPriority = [.anyData, .loading, .error]
+
         showUser(nil)
 
         searchBar.becomeFirstResponder()
@@ -144,7 +146,7 @@ class UserViewController: UIViewController, UISearchBarDelegate, ResourceObserve
 
         // Setting the repositoriesResource property of the embedded VC triggers load & display of the user’s repos.
 
-        repoListVC?.repositoriesResource = repositoriesResource
+        repoListVC?.$repositories.resource = repositoriesResource
         usernameLabel.text = title
     }
 

Siesta.podspec

@@ -79,6 +79,12 @@ Pod::Spec.new do |s|
     s.exclude_files = "**/Info*.plist"
   end
 
+  s.subspec "Tools" do |s|
+    s.source_files = "Source/SiestaTools/**/*"
+    s.exclude_files = "**/Info*.plist"
+    s.dependency "Siesta/Core"
+  end
+
   s.subspec "UI" do |s|
     s.ios.source_files = "Source/SiestaUI/**/*.{swift,m,h}"
     s.dependency "Siesta/Core"