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So in the last lesson, we learned about using the Firebase Authentication Module to register our very
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first user,
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this 1@2.com person.
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Now, we're going to look at the login routes.
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So in this case, it's this screen right here and we're going to be doing pretty much the same thing
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as what we did in the register screen.
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We're going to take the email and password that they've typed in, and in the moment, when they press on
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the login button, we're going to take their details through to Firebase. And we're going to be using
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a login method to check that email and password against what we've got stored in our fFrebase Authentication
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database.
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And if that was successful, then we're again going to take them straight to the Chart View Controller.
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So this is the case where after the user registers for the first time, the next time, they use our service
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they're always going to be accessing it through the login route.
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So let's go ahead and tackle this.
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If we head back to the documentation and we go to authentication, iOS password authentication, we can
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skip all the parts that we've already done and head over to the sign in user with an email address
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and password section.
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We've already done step one and step two.
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We now have to move on to step three.
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So the method is called signInWithEmail and password.
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And, again, it takes two arguments or inputs.
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One is the e-mail that they've registered with and another is the password that they've registered with.
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And once this closure completes, we end up with an authentication result and an error
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if there was one.
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So the user's account data will live in this authResult object that we get back and we can use it inside
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this closure block or we can check to see if there were any errors.
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Again, I'm gonna go ahead and copy this code, making sure that you're copying the Swift code and not the
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Objective-C code which will look very strange anyways. And heading back to our app,
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we're going to go to the LoginViewController.swift and we're going to put that code inside the
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loginPressed IBAction.
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So that, of course, relates to this particular button when it gets pressed.
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And what we want to happen is to trigger this sign in with email and password method.
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So, again, we need to tell this file that we want to use the Firebase module, so that we can use the Auth object
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and we also have to supply an email and password. And I want to quickly pause here and pose a
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challenge to you.
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See if you can add the code to retrieve the tags that the user typed into the email and the password fields,
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then you should only call the sign and method if neither the email nor the password text is equal
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to nil.
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I'll give you a few seconds to pause the video before I show you the solution.
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Ready?
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Here's the solution.
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I'm going to do the same thing that we did before to use optional binding to get out the email text
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and password text.
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So I'm going to write "if let email = emailTextField.text, and then add a comma,
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and let password = passwordTextField.text, and then we're going to wrap all of this authentication
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code inside a set of curly brackets like so.
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And now we're ready to tackle this block.
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And that's the solution to the challenge.
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The code we wrote is very similar to what we did in the RegisterViewController.
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Now, you might have noticed that this particular signIn method actually looks a little bit different
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from the create user method that we got from Firebase earlier on.
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And the extra bits are this part, the "weak self," and also this "guard" statement, and this is just a little
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bit of code that Firebase has actually left in here which is actually slightly outdated. The latest syntax
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would look something like this.
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And what it does is it avoids a retained cycle in the cases where we're actually referring to the view
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controller within our closure,
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and we're going to be destroying this view controller before this closure completes.
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So if you're interested in getting more details on this and why it is that we don't actually need this
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part or this part in our code, then I've linked to a number of resources for you to check out. And I have
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to warn you it's quite complex and the rabbit hole goes quite deep,
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but I found some resources that explain this topic quite well.
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So if you're interested in the nitty-gritty details, then be sure to check it out.
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All right.
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So coming back to our Authentication signIn method, we want to do the same thing that we did before
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which is to check if there was an error.
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So if let e = error, then in this case, I'm going to simply just print the error,
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but, of course, we could also handle this error by presenting it to the user, in which case we would have
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to take a look at the reference for "FIRAuthErrors" to see all of the different error codes, create a
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switch statement that checks for which one we're gettingm and then turn all of those error codes into
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a message that's useful for the user, and then present it in some sort of alerts.
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Now in my case, I'm just going to print it out for the developer to see.
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But if we know that the error is equal to nil, then we can go ahead and add an "else" statement to proceed
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with the login process.
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So in this case, what we're gonna do is we're going to keep the login screen in our navigation stack.
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So at this point, they've got the welcome screen at the bottom,
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the login screen next, and then on top of that, we're going to present the next screen which is the
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ChatViewController. And I want to pose this to you as another challenge. See if you can write the code that
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navigates the ChatViewController when signIn has been successful. I'll give you a few seconds to pose
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a video before I show you the solution.
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Ready?
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Here's the solution.
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We're going to navigate to the ChatViewController in the same way as we did in the RegisterViewController
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which is to perform a segue with a particular identifier.
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And in our case, that segue is this one which we named LoginToChat.
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So I'm just going to copy it from here to minimize the possibility of typos. And then down here in this
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"else" statement, I'm going to say performSegue withIdentifier and sender is "self."
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This is the starting point of our segue.
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And the final thing we have to do is to add the "self" in front of our performSegue method call, and
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that's the solution to the challenge.
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We're now ready to run our app and test it out, so instead of going to the register page, I'm going to
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go into the login page. And here I'm going to use the credentials that I used previously to register
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which is a user with email 1@2.com and their password was
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1, 2, 3, 4, 5, 6.
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Because six is the minimum number of characters I have to supply Firebase with in order for it to accept
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it as a password.
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So, now my email is going to be 1@2.com and my password: 1, 2, 3, 4, 5, 6,
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and then I'm going to click Log In.
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And as you can see, the login process was successful.
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I didn't get any error messages and it performed to that segue taking me to the Chat View Controller right
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here.
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So that's how we log in our users. In the next lesson,
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we're going to be covering the logout route so that we'll be able to log in users, register users, and
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also log them out back to the welcome screen.
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So for all of that and more, I'll see you on the next lesson.