在Xcode中创建登录/注册视图

Question

I am making an app for iOS in Xcode.

My question is: How do I make the app show the signup/login view when it is needed, but not show it when the user is already logged in? Is it communicating with the database every time the app launches? I am planning on using MySQL for creating a database with simple users (username, score, friends). Is there a tutorial that will show me the steps for doing this? I have no experience with databases.

Help is appreciated.

Answer 1

You need to look at a bunch of tutorials, I recommend these guys:

https://www.raywenderlich.com

They have free tutorials in ObjC and Swift as well as video courses!

Answer 2

A REST API normally respond with a 401 (Unauthorized code) if there isn't a valid/logged user, so every time I get a 401 I show a login within a modal view.

So when you load the app, call a GET currentUser endpoint, if it returns a 401 the app will show the login, if not, the app will show the default rootViewController .

I like this way because if for any reason, your session is no longer valid, the app will show the login view.

Answer 3

I'm gonna give you a comprehensive answer.

Don't use NSUserDefaults and don't store password it's a bad solution

NSUserDefaults data is not encrypted, it may cause security issue.

Let's create a structured user class instead

When the user logged in, you will need to make sure you have access to user data throughout the app so you can get the data on any screen when you need it.

To achieve this, we need to make a great structure to organize this properly. Remember that current user and another users are both "user" so we will use the same class.

Create a class and name it "EDUser" (you can choose other name if you want).
This class will contain a user information (either current user or other user).
More than that, this class will have capability to log the user in.

Here's a picture of what the class might look like:

class EDUser {
    var firstName: String
    var lastName: String?
    var birthDate: NSDate?

    init(firstName: String, lastName: String?, birthDate: NSDate?) {
        self.firstName = firstName
        self.lastName = lastName
        self.birthDate = birthDate
    }
}

// MARK: - Accessor

extension EDUser {
    class var currentUser: EDUser? {
        get {
            return loadCurrentUserFromDisk()
        }
        set {
            saveCurrentUserToDiskWithUser(newValue)
        }
    }
}

// MARK: - Log in and out

extension EDUser {
    class func loginWithUsername(username: String,
                           andPassword password: String,
                           callback: (EDUser?, NSError) -> Void) {
        // Access the web API
        var parameters = [
            "username": username,
            "password": password
        ]
        YourNetworkingLibrary.request(.POST,
                          "https://api.yourwebsite.com/login",
                          parameters: parameters).responseJSON { 
            response in

            if response.statusCode == .Success {
                let user = EDUser(firstName: response["firstName"],
                       lastName: response["lastName"],
                       birthDate: NSDate.dateFromString(response["birthDate"]))
                currentUser = user
                callback(currentUser, nil)
            } else {
                callback(nil, yourError)
            }
        }
    }

    class func logout() {
        deleteCurrentUserFromDisk()
    }
}

// MARK: - Data

extension EDUser {
    class private func saveCurrentUserToDiskWithUser(user: EDUser) {
        // In this process, you encode the user to file and store it
    }

    class private func loadCurrentUserFromDisk() -> EDUser? {
        // In this process, you get the file and decode that to EDUser object
        // This function will return nil if the file is not exist
    }

    class private func deleteCurrentUserFromDisk() {
        // This will delete the current user file from disk
    }
}

// MARK: - Helper

extension NSDate {
    class func dateFromString(string: String) -> NSDate {
        // convert string into NSDate
    }
}

Use Case

Now with everything in place, we can use it like this

Non-blocking logging in process

EDUser.loginWithUsername(username: "edward@domain.com",
                         password: "1234") {
    user, error in

    if error == nil {
        // Login succeeded
    } else {
        // Login failed
    }
}

Logging out

EDUser.logout()

Check whether the user is logged in

if EDUser.currentUser != nil {
    // The user is logged in
} else {
    // No user logged in
    // Show the login screen here
}

Get current user data on any screen

if let currentUser = EDUser.currentUser {
    // do something with current user data
}

Store other user as object

let user = EDUser(firstName: "Edward",
                  lastName: "Anthony",
                  birthDate: NSDate())