feat: SSE / real time flags support #32 (#67)

* Update example app with the latest local SDK version

* Checkpoint commit, SSE connection up and running, need to implement the decoding and logic

* Attempt to decode the SSE data

* Initial implementation of the logic from the Kotlin implementation

* Add a SwiftUI view to the example app to show real-time updates to the flags

* Fix an issue with taking too many event stream updated-at times

* Swift lint and tidy up

* Add some unit tests for the SSEManager class and also change the reconnection logic to use a backoff timer

* Tidy and document SSEManager

* A bit of a tidy and swift linting

* Removed some commented-out code and put some back in

* Run swift format and update the swift format package

* Update FlagsmithClient/Tests/SSEManagerTests.swift

Co-authored-by: Matthew Elwell <[email protected]>

* Updated use of API Key -> env

* Remove the unnecessary Podfile.lock from the example app

---------

Co-authored-by: Matthew Elwell <[email protected]>

Author: gazreese

.gitignore

@@ -48,3 +48,7 @@ Carthage/Build
 # hence it is not needed unless you have added a package configuration file to your project
 .swiftpm
 .build
+
+# This was causing confusion on PRs and is really just a record of the last time the example
+# pods were re-built from scratch. It's not useful to keep in the repo.
+Example/Podfile.lock

Example/FlagsmithClient.xcodeproj/project.pbxproj

@@ -7,6 +7,7 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		7F76D20A2C9852510028470B /* SwiftUIView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7F76D2092C9852510028470B /* SwiftUIView.swift */; };
 		C87CA15C7294632245730C64 /* Pods_FlagsmithClient_Example.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = C9F7BEB767BE008D76723DD6 /* Pods_FlagsmithClient_Example.framework */; };
 		DAED1E94268DBF9100F91DBC /* ViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = DAED1E8C268DBF9100F91DBC /* ViewController.swift */; };
 		DAED1E95268DBF9100F91DBC /* LaunchScreen.xib in Resources */ = {isa = PBXBuildFile; fileRef = DAED1E8D268DBF9100F91DBC /* LaunchScreen.xib */; };
@@ -18,6 +19,7 @@
 /* Begin PBXFileReference section */
 		5357A0EF6DA00FB7B1E84F8C /* Pods-FlagsmithClient_Example.release.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-FlagsmithClient_Example.release.xcconfig"; path = "Target Support Files/Pods-FlagsmithClient_Example/Pods-FlagsmithClient_Example.release.xcconfig"; sourceTree = "<group>"; };
 		607FACD01AFB9204008FA782 /* FlagsmithClient_Example.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = FlagsmithClient_Example.app; sourceTree = BUILT_PRODUCTS_DIR; };
+		7F76D2092C9852510028470B /* SwiftUIView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SwiftUIView.swift; sourceTree = "<group>"; };
 		9DFD4B33E10902546A38D90F /* Pods-FlagsmithClient_Example.debug.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-FlagsmithClient_Example.debug.xcconfig"; path = "Target Support Files/Pods-FlagsmithClient_Example/Pods-FlagsmithClient_Example.debug.xcconfig"; sourceTree = "<group>"; };
 		C4197E729B096AA93F72A537 /* LICENSE */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text; name = LICENSE; path = ../LICENSE; sourceTree = "<group>"; };
 		C9F7BEB767BE008D76723DD6 /* Pods_FlagsmithClient_Example.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = Pods_FlagsmithClient_Example.framework; sourceTree = BUILT_PRODUCTS_DIR; };
@@ -96,6 +98,7 @@
 				DAED1E8F268DBF9100F91DBC /* Main.storyboard */,
 				DAED1E91268DBF9100F91DBC /* Images.xcassets */,
 				DAED1E92268DBF9100F91DBC /* AppDelegate.swift */,
+				7F76D2092C9852510028470B /* SwiftUIView.swift */,
 			);
 			path = FlagsmithClient;
 			sourceTree = "<group>";
@@ -220,6 +223,7 @@
 			files = (
 				DAED1E98268DBF9100F91DBC /* AppDelegate.swift in Sources */,
 				DAED1E94268DBF9100F91DBC /* ViewController.swift in Sources */,
+				7F76D20A2C9852510028470B /* SwiftUIView.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

Example/FlagsmithClient.xcodeproj/xcshareddata/xcschemes/FlagsmithClient_Example.xcscheme

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "1320"
+   LastUpgradeVersion = "1540"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"

Example/FlagsmithClient/AppDelegate.swift

@@ -8,6 +8,9 @@
 
 import UIKit
 import FlagsmithClient
+#if canImport(SwiftUI)
+    import SwiftUI
+#endif
 
 func isSuccess<T, F>(_ result: Result<T, F>) -> Bool {
     if case .success = result { return true } else { return false }
@@ -43,6 +46,9 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
 
     // set analytics on or off
     Flagsmith.shared.enableAnalytics = true
+    
+    // Enable real time updates
+    Flagsmith.shared.enableRealtimeUpdates = true
 
     // set the analytics flush period in seconds
     Flagsmith.shared.analyticsFlushPeriod = 10
@@ -65,6 +71,15 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
 
     // Flagsmith.shared.setTrait(Trait(key: "<my_key>", value: "<my_value>"), forIdentity: "<my_identity>") { (result) in print(result) }
     // Flagsmith.shared.getIdentity("<my_key>") { (result) in print(result) }
+    
+    // Launch SwiftUIView
+    if #available(iOS 13.0, *) {
+      let swiftUIView = SwiftUIView()
+      window = UIWindow(frame: UIScreen.main.bounds)
+      window?.rootViewController = UIHostingController(rootView: swiftUIView)
+      window?.makeKeyAndVisible()
+    }
+    
     return true
   }
 

Example/FlagsmithClient/Base.lproj/LaunchScreen.xib

@@ -29,9 +29,6 @@
             <constraints>
                 <constraint firstItem="kId-c2-rCX" firstAttribute="centerY" secondItem="iN0-l3-epB" secondAttribute="bottom" multiplier="1/3" constant="1" id="5cJ-9S-tgC"/>
                 <constraint firstAttribute="centerX" secondItem="kId-c2-rCX" secondAttribute="centerX" id="Koa-jz-hwk"/>
-                <constraint firstAttribute="bottom" secondItem="8ie-xW-0ye" secondAttribute="bottom" constant="20" id="Kzo-t9-V3l"/>
-                <constraint firstItem="8ie-xW-0ye" firstAttribute="leading" secondItem="iN0-l3-epB" secondAttribute="leading" constant="20" symbolic="YES" id="MfP-vx-nX0"/>
-                <constraint firstAttribute="centerX" secondItem="8ie-xW-0ye" secondAttribute="centerX" id="ZEH-qu-HZ9"/>
                 <constraint firstItem="kId-c2-rCX" firstAttribute="leading" secondItem="iN0-l3-epB" secondAttribute="leading" constant="20" symbolic="YES" id="fvb-Df-36g"/>
             </constraints>
             <nil key="simulatedStatusBarMetrics"/>

Example/FlagsmithClient/SwiftUIView.swift

@@ -0,0 +1,68 @@
+//
+//  SwiftUIView.swift
+//  FlagsmithClient_Example
+//
+//  Created by Gareth Reese on 16/09/2024.
+//  Copyright © 2024 CocoaPods. All rights reserved.
+//
+
+#if canImport(SwiftUI)
+    import SwiftUI
+#endif
+import FlagsmithClient
+
+@available(macOS 10.15, iOS 13.0, tvOS 13.0, watchOS 7.0, *)
+struct SwiftUIView: View {
+    @State private var flags: [Flag] = []
+    @State private var isLoading = true
+
+    let flagsmith = Flagsmith.shared
+
+    var body: some View {
+        VStack {
+            if isLoading {
+                ProgressView()
+            } else {
+                Text("Feature Flags")
+                    .font(.title)
+                    .padding()
+                List(flags, id: \.feature.name) { flag in
+                    HStack {
+                        Text("\(flag.feature.name): \(flag.value)")
+                        Spacer()
+                        Text("\(flag.enabled ? "✅" : "❌")")
+                    }
+                }
+            }
+        }
+        .onAppear {
+            initializeFlagsmith()
+            subscribeToFlagUpdates()
+        }
+    }
+
+    func initializeFlagsmith() {
+        // Fetch initial flags
+        flagsmith.getFeatureFlags { result in
+            DispatchQueue.main.async {
+                switch result {
+                case .success(let fetchedFlags):
+                    flags = fetchedFlags
+                case .failure(let error):
+                    print("Error fetching flags: \(error)")
+                }
+                isLoading = false
+            }
+        }
+    }
+
+    func subscribeToFlagUpdates() {
+        Task {
+            for await updatedFlags in flagsmith.flagStream {
+                DispatchQueue.main.async {
+                    flags = updatedFlags
+                }
+            }
+        }
+    }
+}