What does sign_in of devise do

Question

I am making rails api authentication using devise but could not understand properly what sign_in of devise is doing for us.

I have session controller with create method for sign in a user.

def create 
 user_email = params[:session][:email]
 user_password = params[:session][:password]
 user = user_email.present? && User.find_by(email: user_email)
 if user.valid_password?(user_password)
   sign_in user, store: false   /* exactly this line */
   render json: user, status: 200, location: [:api, user]
 else
   render json: { errors: "Invalid email or password" }, status: 422
 end
end

On rubydoc its description is written like this

Sign in a user that already was authenticated. This helper is useful for logging users in after sign up. All options given to sign_in is passed forward to the set_user method in warden.

But it is not clear to me. Thanks.

Answer 1

sign_in is for when you already have a User object that you created or loaded/authenticated yourself and thus want to store in the session as the authenticated user for the rest of the current as well as upcoming requests.

If you look at the source code for the default Devise SessionsController you'll see that it also uses sign_in to log in a user.

Devise is a layer over warden, so you might want to look at its documentation to understand this level of functionality. As the Devise documentation you quoted states, sign_in just calls the set_user method from warden. What Devise adds on top is a lot of convenience like the ability to work with multiple scopes and various warden authentication strategies.