Update when the app launches or becomes active and it's been a day since last update

Xcodes/Backend/AppState.swift

@@ -167,12 +167,22 @@ class AppState: ObservableObject {
         updatePublisher = update()
             .sink(
                 receiveCompletion: { [unowned self] _ in
+                    Current.defaults.setDate(Current.date(), forKey: "lastUpdated")
                     self.updatePublisher = nil
                 },
                 receiveValue: { _ in }
             )
     }
     
+    func updateIfNeeded() {
+        guard
+            let lastUpdated = Current.defaults.date(forKey: "lastUpdated"),
+            // This is bad date math but for this use case it doesn't need to be exact
+            lastUpdated < Current.date().addingTimeInterval(-60 * 60 * 24) 
+        else { return }
+        update() as Void
+    }
+    
     private func update() -> AnyPublisher<[Xcode], Never> {
         signInIfNeeded()
             .flatMap {

Xcodes/Backend/Environment.swift

@@ -19,6 +19,7 @@ public struct Environment {
     public var logging = Logging()
     public var keychain = Keychain()
     public var defaults = Defaults()
+    public var date: () -> Date = Date.init
 }
 
 public var Current = Environment()
@@ -153,6 +154,16 @@ public struct Defaults {
         string(key)
     }
     
+    public var date: (String) -> Date? = { Date(timeIntervalSince1970: UserDefaults.standard.double(forKey: $0)) }
+    public func date(forKey key: String) -> Date? {
+        date(key)
+    }
+    
+    public var setDate: (Date?, String) -> Void = { UserDefaults.standard.set($0?.timeIntervalSince1970, forKey: $1) }
+    public func setDate(_ value: Date?, forKey key: String) {
+        setDate(value, key)
+    }
+    
     public var set: (Any?, String) -> Void = { UserDefaults.standard.set($0, forKey: $1) }
     public func set(_ value: Any?, forKey key: String) {
         set(value, key)

Xcodes/Frontend/XcodeList/XcodeListView.swift

@@ -106,7 +106,6 @@ struct XcodeListView: View {
         }
         .navigationSubtitle(Text("Updated \(Date().addingTimeInterval(-600), style: .relative) ago"))
         .frame(minWidth: 200, maxWidth: .infinity, minHeight: 300, maxHeight: .infinity)
-        .onAppear(perform: appState.update)
         .alert(item: $appState.error) { error in
             Alert(title: Text(error.title), 
                   message: Text(verbatim: error.message), 

Xcodes/XcodesApp.swift

@@ -4,12 +4,21 @@ import AppKit
 @main
 struct XcodesApp: App {
     @NSApplicationDelegateAdaptor(AppDelegate.self) var appDelegate: AppDelegate
+    @SwiftUI.Environment(\.scenePhase) private var scenePhase: ScenePhase
     @StateObject private var appState = AppState()
     
     var body: some Scene {
         WindowGroup("Xcodes") {
             XcodeListView()
                 .environmentObject(appState)
+                // This is intentionally used on a View, and not on a WindowGroup, 
+                // so that it's triggered when an individual window's phase changes instead of all window phases.
+                // When used on a View it's also invoked on launch, which doesn't occur with a WindowGroup. 
+                .onChange(of: scenePhase) { newScenePhase in
+                    if case .active = newScenePhase {
+                        appState.updateIfNeeded()
+                    }
+                }
         }
         .commands {
             CommandGroup(replacing: .appInfo) {