In this codealong lab, we'll build a Sinatra application that will allow users to sign up for, log into, and then log out of your application.
- Explain how logging in to an application stores a user's ID into a
session
hash - Set up a root path and homepage for the application
- Build a user sign-up flow with a Users model that signs in and logs in a user
- Log out the user by clearing the
session
hash
What does it mean for a user to 'log in'? The action of logging in is the simple
action of storing a user's ID in the session
hash. Here's a basic user login
flow:
- User visits the login page and fills out a form with their email and
password. They hit 'submit' to
POST
that data to a controller route. - That controller route accesses the user's email and password from the
params
hash. That info is used to find the appropriate user from the database with a line such asUser.find_by(email: params[:email], password: params[:password])
. Then, that user's ID is stored as the value ofsession[:user_id]
. - As a result, we can introspect on the
session
hash in any other controller route and grab the current user by matching up a user ID with the value insession[:user_id]
. That means that, for the duration of the session (i.e., the time between when someone logs in to and logs out of your app), the app will know who the current user is on every page.
For the time being, we will simply store a user's password in the database in its raw form. However, that is not safe! In an upcoming lesson, we'll learn about password encryption: the act of scrambling a user's password into a super-secret code and storing a decrypter that will be able to match up a plaintext password entered by a user with the encrypted version stored in a database.
What does it mean to log out? Conceptually, it means we are terminating the
session, the period of interaction between a given user and our app. The action
of 'logging out' is really just the action of clearing all of the data,
including the user's ID, from the session
hash. Luckily for us, there is
already a Ruby method for emptying a hash: #clear
.
Before a user can sign in, they need to sign up! What does it mean to 'sign up'?
A new user submits their information (for example, their name, email, and
password) via a form. When that form gets submitted, a POST
request is sent to
a route defined in the controller. That route will have code that does the
following:
- Gets the new user's name, email, and password from the
params
hash. - Uses that info to create and save a new instance of
User
. For example:User.create(name: params[:name], email: params[:email], password: params[:password])
. - Signs the user in once they have completed the sign-up process. It would be
annoying if you had to create a new account on a site and then sign in
immediately afterwards. So, in the same controller route in which we create a
new user, we set the
session[:user_id]
equal to the new user's ID, effectively logging them in. - Finally, we redirect the user somewhere else, such as their personal homepage.
Our file structure looks like this:
-app
|- controllers
|- application_controller.rb
|- models
|- user.rb
|- views
|- home.erb
|- registrations
|- signup.erb
|- sessions
|- login.erb
|- users
|- home.erb
-config
-db
-spec
...
The app
folder contains the models, views and controllers that make up the
core of our Sinatra application. Get used to seeing this setup. It is
conventional to group these files under an app
folder.
-
The
get '/registrations/signup'
route has one responsibility: render the sign-up form view. This view can be found inapp/views/registrations/signup.erb
. Notice we have separate view sub-folders to correspond to the different controller action groupings. -
The
post '/registrations'
route is responsible for handling thePOST
request that is sent when a user hits 'submit' on the sign-up form. It will contain code that gets the new user's info from theparams
hash, creates a new user, signs them in, and then redirects them somewhere else. -
The
get '/sessions/login'
route is responsible for rendering the login form. -
The
post '/sessions'
route is responsible for receiving thePOST
request that gets sent when a user hits 'submit' on the login form. This route contains code that grabs the user's info from theparams
hash, looks to match that info against the existing entries in the user database, and, if a matching entry is found, signs the user in. -
The
get '/sessions/logout'
route is responsible for logging the user out by clearing thesession
hash. -
The
get '/users/home'
route is responsible for rendering the user's homepage view.
The models
folder is pretty straightforward. It contains one file because we
only have one model in this app: User
.
The code in app/models/user.rb
will be pretty basic. We'll validate some of
the attributes of our user by writing code that makes sure no one can sign up
without inputting their name, email, and password. More on this later.
This folder has a few sub-folders we want to take a look at. Since we have
different controllers responsible for different functions/features, we want our
views
folder structure to match up.
- The
views/registrations
sub-directory contains one file, the template for the new user sign-up form. That template will be rendered by theget '/registrations/signup'
route in our controller. This form willPOST
to thepost '/registrations'
route in our controller. - The
views/sessions
sub-directory contains one file, the template for the login form. This template is rendered by theget '/sessions/login'
route in the controller. The form on this page sends aPOST
request that is handled by thepost '/sessions'
route. - The
views/users
sub-directory contains one file, the template for the user's homepage. This page is rendered by theget '/users/home'
route in the controller. - We also have a
home.erb
file in the top level of theviews
directory. This is the page rendered by the root route,get '/'
.
Our User
model has a few attributes: a name, email, and password.
Use rake db:create_migration
to write a migration that creates a Users
table
with columns for name, email, and password. Run
rake db:migrate SINATRA_ENV=test
and then run your test suite.
You'll see that you're passing a number of tests, including these:
User
is invalid without a name
is invalid without a email
is invalid without an password
First things first, let's set up our root path and homepage.
Open up app/controllers/application_controller.rb
and check out the get '/'
route. This route should render the app/views/home.erb
page with the following
code:
erb :home
Run your test suite again with learn
or rspec
in the command line and you
should be passing these two tests:
ApplicationController
homepage: GET /
responds with a 200 status code
renders the homepage view, 'home.erb'
Start up your app by running shotgun
in the terminal. Visit the homepage at
localhost:9393. You should see a message that welcomes
you to Hogwarts and shows you a link to sign up and a link to log in.
Let's look at the code behind this view. Open up app/views/home.erb
and you
should see the following:
<h1>Welcome to Hogwarts</h1>
<h4>Please sign up or log in to access your @hogwarts.edu email account</h4>
<a href="/registrations/signup">Sign Up</a>
<a href="/sessions/login">Log In</a>
Notice that we have two links, the "Sign Up" link and the "Log In" link. Let's take a closer look:
- The 'href' (destination) value of the first link is
/registrations/signup
. This means that the link points to theget '/registrations/signup'
route. - The 'href' value of the second link is
/sessions/login
. This means that the link points to theget '/sessions/login'
route.
Let's move on to step 2, the building of our user sign-up flow.
In your controller you should see two routes dedicated to sign-up. Let's take a
look at the first route, get '/registrations/signup'
, which is responsible for
rendering the sign-up template. Add the following code in this route:
get '/registrations/signup' do
erb :'/registrations/signup'
end
Navigate to localhost:9393/registrations/signup. You should see a page that says 'Sign Up Below:'. Let's make a sign-up form!
Open up app/views/registrations/signup.erb
. Our signup form needs fields for
name, email, and password. It needs to POST
data to the '/registrations'
path, so your form action should be '/registrations'
and your form method
should be POST
.
Once you've written your form, go ahead and add the line puts params
inside
the post '/registrations'
route in the controller. Then, fill out the form in
your browser and hit the "Sign Up"
button.
Hop on over to your terminal and you should see the params outputted there. It should look something like this (but with whatever info you entered into the form):
{"name"=>"Beini Huang", "email"=>"[email protected]", "password"=>"password"}
Okay, so we're inside our post '/registrations'
route, and we have our
params
hash that contains the user's name, email, and password. Inside the
post '/registrations'
route, place the following code:
@user = User.new(name: params["name"], email: params["email"], password: params["password"])
@user.save
We did it! We registered a new user! Now we just need to sign them in. On the
following line, set the session[:user_id]
equal to our new user's ID:
session[:user_id] = @user.id
Take a look at the last line of the method:
redirect '/users/home'
Now that we've signed up and logged in our user, we want to take them to their homepage.
Go ahead and run the test suite again and you should see that almost all of the user sign-up tests are passing.
Open up the view file: app/views/users/home.erb
and look at the following line
of code:
"Welcome, <%=@user.name%>!"
Looks like this view is trying to operate on a @user
variable. We know that
the only variables that a view can access are instance variables set in the
controller route that renders that particular view page. Let's take a look at
the route in our controller that corresponds to the /users/home
view.
Remember, after a user signs up and is signed in via the code we wrote in the
previous step, we redirect to the '/users/home'
path. Let's check out that
route right now.
Again, take a look at the controller. You should see the get '/users/home'
route. First, this route finds the current user based on the ID value stored in
the session
hash. Then, it sets an instance variable, @user
, equal to that
found user, allowing us to access the current user in the corresponding view
page. Let's set it up:
get '/users/home' do
@user = User.find(session[:user_id])
erb :'/users/home'
end
Run the tests again and we should be passing all of our user sign up tests.
Go back to your homepage and look at the second of the two links:
<a href="/sessions/login">Log In</a>
This is a link to the get '/sessions/login'
route. Checkout the two routes
defined in the controller for logging in and out. We have a
get '/sessions/login'
route and a post '/sessions'
route.
The get /sessions/login'
route renders the login view page. Restart your app
by executing Ctrl + C
and then typing shotgun
in your terminal. Navigate
back to the root page, localhost:9393, and click on
the 'Log In' link. It should take you to a page that says 'Log In Below:'. Let's
create our login form!
Open up app/views/sessions/login.erb
. We need a form that sends a POST
request to /sessions
and has input fields for email and password. Don't forget
to add a submit button that says 'Log In'. Then, to test that everything is
working as expected, place the line puts params
in the post '/sessions'
route. In your browser, fill out the form and hit 'Log In'.
In your terminal, you should see the outputted params
hash looking something
like this (but with whatever information you entered into the login form):
{"email"=>"[email protected]", "password"=>"password"}
Inside the post '/sessions'
route, let's add the lines of code that will
find the correct user from the database and log them in by setting the
session[:user_id]
equal to their user ID.
@user = User.find_by(email: params["email"], password: params["password"])
session[:user_id] = @user.id
Notice that the last line of the route redirects the user to their homepage:
redirect '/users/home'
We already coded the '/users/home'
route in the controller to retrieve the
current user based on the ID stored in session[:user_id]
.
What if our user doesn't provide the right email or password? What should our site show them next? Well, we should probably give them another shot at logging in. We can do so with a bit of conditional logic:
post '/sessions' do
@user = User.find_by(email: params[:email], password: params[:password])
if @user
session[:user_id] = @user.id
redirect '/users/home'
end
redirect '/sessions/login'
end
Run the test suite again and you should be passing the user login tests.
Open up app/views/users/home.erb
and check out the following link:
<a href="/sessions/logout">Log Out</a>
We have a link that takes us to the get '/sessions/logout'
route, which is
responsible for logging us out by clearing the session
hash.
In the get '/sessions/logout'
route in the controller, put:
session.clear
Run the test suite again, and you should be passing everything.
Phew! This was a big code-along, and we were introduced to some new concepts. Before moving on, play around with your app a bit. Practice signing up, logging out, and logging in, and get used to the general flow.
There's a lot to think about here, but here are a few takeaways:
- Separate out your views into sub-folders according to their different concerns / controller routes.
- Signing up for an app is nothing more than submitting a form, grabbing data
from the
params
hash, and using it to create a new user. - Logging in is nothing more than locating the correct user and setting the
:id
key in thesession
hash equal to their user ID. - Logging out is accomplished by clearing all of the data from the
session
hash.
Another important takeaway from this lab is a general understanding of the flow of information between the different routes and views of an application. If you're still confused by the flow of signing up and logging in/out, try drawing it out. Can you map out where your web requests go from the point at which you click the "Sign Up" link all the way through until you log out and then attempt to log back in? Give it a shot.