取当前版本号
let currentVersion = Bundle.main.infoDictionary?["CFBundleShortVersionString"] as? String ?? ""
取之前的版本号
let docDir = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]
let path: String = (docDir as? NSString)?.appendingPathComponent("path.json") ?? ""
let sandBoxVersion = try? (String(contentsOfFile: path))
将当前版本号保存在沙盒中
try? currentVersion.write(toFile: path, atomically: true, encoding: .utf8)
返回两个版本号，是否一致
return currentVersion != sandBoxVersion
