title: Single Table Inheritance Errors - ActiveRecord::SubclassNotFound
body: <p>My intent is to implement STI with two types: Staff and Clinician. My previous implementation was using roles with enums, and after doing my best to follow answers to similar questions, take out all references in tests etc. to enum roles and replace with references to types , I am getting many versions of the following error when I run my testing suite:</p>
  
  <pre><code>ERROR["test_valid_signup_information_with_account_activation", UsersSignupTest, 1.01794000000001]
   test_valid_signup_information_with_account_activation#UsersSignupTest (1.02s)
  ActiveRecord::SubclassNotFound:         ActiveRecord::SubclassNotFound: The single-table inheritance mechanism failed to locate the subclass: 'Staff'. This error is raised because the column 'type' is reserved for storing the class in case of inheritance. Please rename this column if you didn't intend it to be used for storing the inheritance class or overwrite User.inheritance_column to use another column for that information.
              app/controllers/users_controller.rb:19:in `create'
              test/integration/users_signup_test.rb:27:in `block (2 levels) in &lt;class:UsersSignupTest&gt;'
              test/integration/users_signup_test.rb:26:in `block in &lt;class:UsersSignupTest&gt;'
  </code></pre>
  
  <p>Here are a couple areas where I am confused that could potentially be hiding issues:</p>
  
  <p>In my user model user.rb, I think I am defining the sub Classes correctly (Staff and Clinician), but I'm unsure if I'm wrapping everything correctly. Does all the other code have to be contained in one of these classes? Am I misusing "end"?</p>
  
  <pre><code>class User &lt; ApplicationRecord
  end
  
  class Staff &lt; User
  end
  
  class Clinician &lt; User
  end
  
  belongs_to :university
  has_many :referral_requests
  
  
  
  
    attr_accessor :remember_token, :activation_token, :reset_token
    before_save   :downcase_email
    before_create :create_activation_digest
    validates :name,  presence: true, length: { maximum: 50 }
    VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-]+(\.[a-z\d\-]+)*\.[a-z]+\z/i
    validates :email, presence: true, length: { maximum: 255 },
                      format: { with: VALID_EMAIL_REGEX },
                      uniqueness: { case_sensitive: false }
    validates :type, presence: true
    validates :university_id, presence: true, if: lambda { self.type == 'Staff' }
  
    has_secure_password
    validates :password, presence: true, length: { minimum: 6 }, allow_nil: true
  
  
  
  
  
  
    # Returns the hash digest of the given string.
    def User.digest(string)
      cost = ActiveModel::SecurePassword.min_cost ? BCrypt::Engine::MIN_COST :
                                                    BCrypt::Engine.cost
      BCrypt::Password.create(string, cost: cost)
    end
  
    # Returns a random token.
    def User.new_token
      SecureRandom.urlsafe_base64
    end
  
    # Remembers a user in the database for use in persistent sessions.
    def remember
      self.remember_token = User.new_token
      update_attribute(:remember_digest, User.digest(remember_token))
    end
  
    # Returns true if the given token matches the digest.
    def authenticated?(remember_token)
          return false if remember_digest.nil?
      BCrypt::Password.new(remember_digest).is_password?(remember_token)
    end
  
  
    # Forgets a user.
    def forget
      update_attribute(:remember_digest, nil)
    end
  
      # Returns true if the given token matches the digest.
    def authenticated?(attribute, token)
      digest = send("#{attribute}_digest")
      return false if digest.nil?
      BCrypt::Password.new(digest).is_password?(token)
    end
  
    # Activates an account.
    def activate
      update_attribute(:activated,    true)
      update_attribute(:activated_at, Time.zone.now)
    end
  
    # Sends activation email.
    def send_activation_email
      UserMailer.account_activation(self).deliver_now
    end
  
   # Sets the password reset attributes.
    def create_reset_digest
      self.reset_token = User.new_token
      update_attribute(:reset_digest,  User.digest(reset_token))
      update_attribute(:reset_sent_at, Time.zone.now)
    end
  
    # Sends password reset email.
    def send_password_reset_email
      UserMailer.password_reset(self).deliver_now
    end
  
     # Returns true if a password reset has expired.
    def password_reset_expired?
      reset_sent_at &lt; 2.hours.ago
    end
  
   def feed
      ReferralRequest.where("user_id = ?", id)
    end
  
  
   private
  
      # Converts email to all lower-case.
      def downcase_email
      self.email = email.downcase
      end
  
      # Creates and assigns the activation token and digest.
      def create_activation_digest
        self.activation_token  = User.new_token
        self.activation_digest = User.digest(activation_token)
      end
  end
  </code></pre>
  
  <p>Here's the specific test code that is failing (one of many in the test suite that are failing - all the user parameters are defined similarly though). Am I passing the staff parameter appropriately?</p>
  
  <pre><code> test "valid signup information with account activation" do
      get signup_path
      assert_difference 'User.count', 1 do
        post users_path, params: { user: { name:  "Example User",
                                           email: "user@example.com",
                                           university_id: 1 ,
                                           type: "Staff",
                                           password:              "password",
                                           password_confirmation: "password" } }
  </code></pre>
  
  <p>Here is my users table schema:</p>
  
  <pre><code>create_table "users", force: :cascade do |t|
      t.string   "name"
      t.string   "email"
      t.datetime "created_at",                        null: false
      t.datetime "updated_at",                        null: false
      t.string   "password_digest"
      t.string   "remember_digest"
      t.string   "activation_digest"
      t.boolean  "activated",         default: false
      t.datetime "activated_at"
      t.string   "reset_digest"
      t.datetime "reset_sent_at"
      t.integer  "university_id"
      t.integer  "role"
      t.string   "type"
      t.index ["email"], name: "index_users_on_email", unique: true
    end
  </code></pre>
  
  <p>Thanks very much for any ideas! I ask a lot of questions on here but it's only after trying to work through similar answers for quite a while.</p>