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Now that users can sign up, we should let them sign in. Our `login()` view will be pretty straightforward, as will the template.
flask.ext.login is now flask_login
New terms
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login_user- Function to log a user in and set the appropriate cookie so they'll be considered authenticated by Flask-Login
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Our login view is actually going to be a
lot like a registration view.
0:00
We'll show a form, and process it on
submission.
0:04
We'll need to check the password though,
so that adds a new step.
0:06
Let's get to it.
0:09
All right.
So, we need to build a login view.
0:11
As you can probably guess, our login view
actually also needs to have a login form.
0:15
The nice thing is our login form isn't
gonna be all that crazy, and
0:21
it's going to be pretty much the stuff we
used in our registration form.
0:25
So, let's go ahead and make this real
quick.
0:28
Class LoginForm is a form, and it's going
to have two fields.
0:32
So, we're just gonna do email.
0:38
And, we'll do a string field.
0:39
And, we'll say Email.
0:42
And, our validators for
0:43
this will be DataRequired and Email.
0:46
Now, I'd like you to notice I'm not
validating here
0:51
that their email address and password is
right.
0:55
We'll do that in the view.
0:57
And, then we're gonna have a
PasswordField, which will say Password.
0:59
And validators for that will just be that
data is required,
1:03
they have to type in a password.
1:08
Okay, that's our form, pretty simple form.
1:11
Our view is going to be similar to our
other view
1:14
let's see I'm gonna scroll that down, just
so we can see a little more.
1:19
I'll have to go up here, and we need to
add two imports.
1:23
So, we have our LoginManager and we need
to bring in login_user which is
1:27
a function that will check to or that will
actually login our user.
1:31
And, then we need to bring in our bcrypt
library.
1:37
So, from flask.ext.bcrypt import
check_password_hash.
1:40
All right.
1:48
So, now let's go make our login route.
1:50
I'll put it down here, app.route and we'll
say, login.
1:53
And again our methods are GET and POST.
1:59
And we're going to call this login.
2:04
And, the reason we're going to call it
login is because you remember, up here,
2:05
when we specified our login_view, we said
it would be named login.
2:09
So, if you want to change the name, and
2:13
you don't want to call it login, you want
to call it sign in, or, authenticate,
2:14
or something like that, you'll need to
change that up there as well.
2:19
So, our form is going to be
forms.LoginForm().
2:22
And, we're going to say, if
form.validate_on_submit just like before.
2:25
So, now we've got to try and look up the
user.
2:33
So, let's do a try.
2:36
And, we're going to say user equals
models.User.get,
2:37
and models.User.email is equal to
form.email.data.
2:44
Okay?
So, we're going to try and get this user.
2:51
But, if we get a models.DoesNotExist
exception,
2:54
then we want to flash Your email or
password doesn't match.
3:00
And, we want this to have a category of
error.
3:08
Now, why did I say email or
3:11
password, when we know that it's the email
that doesn't exist?
3:13
By doing it with email, we make it fairly
easy for an attacker,
3:17
someone who maybe wants to take over
someone else's account, to figure out,
3:22
okay, that's the right email, that's not
the right email, whatever.
3:26
Like this, they don't know if they got the
email wrong, or the password wrong, so
3:29
it makes it a bit more ambiguous.
3:33
Okay, but if that accept doesn't fire, so
we did get our user,
3:35
then we want to do if check_password_hash.
3:40
And, we want the password of the user, cuz
that's our hash, remember.
3:45
And, the form.password.data, which is the
data they submitted.
3:50
So, if that comes back as true, then we're
going to run login_user with the user.
3:54
So, that user is now gonna be logged in.
4:02
And, we're going to flash, You've been
logged in.
4:03
And, we'll give this a category of
success.
4:10
And, then we want to return a redirect to
index.
4:13
Go back to the home page.
4:19
If that doesn't happen though, if our
password check is incorrect,
4:21
then I actually want to do this all over
again.
4:26
So right there, same message.
4:31
All right, and then if all of that stuff
fails,
4:32
then we're going to render our template,
4:39
and we'll render login.html, and form is
equal to form, okay.
4:44
So, it's not valid, whatever.
4:51
So, let's go build our register, or,
sorry, our login form.
4:54
So, new file, login.html, all right,
template, sorry.
5:00
So, this one is going to be almost
identical to register.
5:05
So, let's actually just copy that, and
paste it in here.
5:09
The one thing we want to change is where
it says Register,
5:14
we want that to say Login.
5:17
And, we probably want to put some links on
here,
5:19
maybe to let people jump from Login to
Register, and back and forth.
5:21
But, for right now, let's not worry about
that too much.
5:25
So, if we come over here and we go to
Login, there's our stuff.
5:28
It's gotta be filled in.
5:33
So, let's use an email address that we
know is not in the account, or
5:35
not an account.
5:40
Login, you get this field is required.
5:41
Let's do, password doesn't even matter.
5:44
And, we get back to here.
5:47
Now, we don't see the flash messages,
5:48
cuz we haven't added those to our template
yet.
5:49
But, you see it's not actually letting me
login.
5:52
But, if I put in one that I know does
exist.
5:55
[BLANK_AUDIO]
5:57
Then, now I went to the front page, and it
asked me if, I want Google to save it.
6:00
I don't, but it's great to know that that
does work.
6:05
Now, that users can log in, we should let
them log out.
6:09
Let's wrap up this stage with a simple
view, just for that.
6:13
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