登录后保存userDefault令牌

Question

I am new in software and I have a question.

I have LoginPage called LoginVC(screenshot as below).When the user opened the app first time, if the member login with his username and password or via Facebook account, next time he opened the app he will pass the login screen and show the "NewsVC" directly. If he logged out, he will see the Login Page again.

According to my investigations I must use UserDefault method and create a local database(for example SQLite). Probably it creates a access token for the entered users. But I don't know how I will do. Maybe there is the question about this problem in this site but because of I don't know in a detailed manner couldn't find the topic.

Can you explain this topic and share an example with a simple Swift 3 code.

Thanks in advance LoginVC ScreenShot

Answer 1

Try following Helper method

Set User ID

func setCurrentLoginID(_ struserid: String) {
    UserDefaults.standard.set(struserid, forKey:"userID")
}

Check User Login or Not

func isUserLoggedIN() -> Bool {
    let str = UserDefaults.standard.object(forKey: "userID") as! String
    return str.characters.count > 0 ? true : false
}

Get User ID

func loggedUserId() -> String {
    let str = UserDefaults.standard.object(forKey: "userID") as? String
    return str == nil ? "" : str!
}

For Logout

func logout() {
    UserDefaults.standard.set(nil, forKey: "userID")
}

Answer 2

Securitywise, it is considered a bad practice to store login tokens in UserDefaults , I'd suggest using Keychain API instead. "Hackers" can relatively easy read data from UserDefaults and use your access token.

Keychain API is a bit hard to use, I'd suggest trying a 3rd party library, here is one example: https://github.com/jrendel/SwiftKeychainWrapper

More info about securing your data on iOS: https://github.com/felixgr/secure-ios-app-dev

If you are just learning - it is OK to use UserDefaults , but once you consider moving your app to production - refactor it to Keychain.

Answer 3

Assuming you wanted to know how to implement this then you can store and get the value like below:-

let default = UserDefaults.standard
default.set(accessToken, forKey: "accessToken")
default.synchronized()
//Now get like this and use guard so that it will prevent your crash if value is nil.
guard let accessTokenValue = default.string(forKey: "accessToken") else {return}
print(accessTokenValue)