Bcrypt and Rails finding an admin user just by entering password -

i'm building app has 3 models (customer, points, admin). customer has points, points belong customer. admin has user_name , password_hash attributes, storing passwords via bcrypt. once customer searches via phone number, points show up. add points, admin has log in password (code of 4 digits) access adding points.

i'm having trouble how find admin via password, not user_name , password.

 class adminscontroller < applicationcontroller   def new    @admin = admin.new  end   def create    @admin = admin.new(admin_params)    if @admin.save      redirect_to root_path    else      flash[:error] = "incorrect data, please check form"      render new_admin_path    end  end   def login    @customer = customer.find(params[:id])   # need input password   params[:password]  # change inputed password password hash  # inputed_password_hash (need here)   # compare password hash password hashes in admin model/database   # see if exists.  # if true, send add points page  # if false, send customer page     if admin.find_by(password_hash: inputed_password_hash)      redirect_to new_points_path    else      render customer_path     end  end     private     def admin_params      params.require(:admin).permit(:user_name, :password, :password_confirmation)    end  end