AppDelegate: Handle major update display.

Riot/Modules/MajorUpdate/MajorUpdateManager.swift

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+/*
+ Copyright 2020 New Vector Ltd
+ 
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+ 
+ http://www.apache.org/licenses/LICENSE-2.0
+ 
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+ */
+
+import Foundation
+
+/// `MajorUpdateManager` is used to indicate if a major update alert should be displayed.
+@objc
+final public class MajorUpdateManager: NSObject {
+    
+    // MARK: - Constants
+    
+    private enum Constants {
+        static var lastMajorAppVersion = AppVersion(bundleShortVersion: "1.0.0", bundleVersion: "0")
+    }
+    
+    // MARK: - Properties
+    
+    // MARK: - Setup & Teardown
+    
+    // MARK: - Public
+    
+    @objc public func shouldShowMajorUpdate() -> Bool {
+        guard let lastUsedAppVersion = AppVersion.lastUsed else {
+            return true
+        }
+        return lastUsedAppVersion.compare(Constants.lastMajorAppVersion) == .orderedAscending
+    }
+}