允许现有用户添加Facebook帐户

Question

In my app, users can login with Facebook using the code from this tutorial . The only issue is I want to allow users who signed up for my app the old fashioned way (As in users go to the signup page and input all their data like email, password, etc and don't log in with Facebook.) to be able to connect their Facebook account with their existing account. I haven't seen any questions on this, and I'm wondering how should I implement this.

Omniauthcallbacks Controller

class Users::OmniauthCallbacksController < Devise::OmniauthCallbacksController
  def all
    user = User.from_omniauth(request.env["omniauth.auth"])
    if user.persisted?
      flash.notice = "Signed in!"
      sign_in_and_redirect user
    else
      session["devise.user_attributes"] = user.attributes
      redirect_to new_user_registration_url
    end
  end
  alias_method :facebook, :all
end

Answer 1

The only issue is I want to allow users who signed up for my app the old fashioned way (As in users go to the signup page and input all their data like email, password, etc and don't log in with Facebook.) to be able to connect their Facebook account with their existing account.

Two possible ways:

1. Use the email address to automatically connect an existing account with that email set when a user uses the Facebook registration flow. (“An account with the email address foo@example.com already exists, do you want to connect your Facebook account with it?”)

2. Have the user log in using your login system, and then offer them a “connect with your Facebook account”-button – and then when they authenticate via Facebook, connect that Facebook ID with the logged in user account.