change password bcrypt with hash and salt on ruby on rails 4.2 - ruby-on-rails-4.2

Question

I'm trying to change the user password using the gem bcrypt and the hash-salt method.
Here's my code where i include my attempt to change password, but it gives me an error of a missing template.
User Controller
def create
#user = User.new(user_params)
end
def change_password
#user = User.find(params[:id])
if #user.password_hash == BCrypt::Engine.hash_secret(params[:current_password], #user.password_salt)
#user.password = params[:password]
#user.save
redirect_to "/users/#{#user.id}"
end
end
private
def user_params
params.require(:user).permit(:email, :password, :password_confirmation)
end
User Model
before_save :encrypt_password
def self.authenticate(email, password)
user = find_by_email(email)
if user && user.password_hash == BCrypt::Engine.hash_secret(password, user.password_salt)
return user
else
return nil
end
end
def encrypt_password
if password.present?
self.password_salt = BCrypt::Engine.generate_salt
self.password_hash = BCrypt::Engine.hash_secret(password, password_salt)
end
end
also, the Routes
patch 'users/:id/change_password' => 'users#change_password'
resources :users
and last but not less important, the form.
<%= form_for(#user, :url => "change_password") do |f| %>
<%= hidden_field(:user, :email, :value => #user.email) %>
<div class="form-group">
<div class="form-group col-md-4"><%= f.label :contraseña_actual %></div>
<div class="form-group col-md-8"><%= f.password_field(:current_password, :class => "form-control") %></div>
</div>
<div class="form-group col-md-4"><%= f.label :nueva_contraseña %></div>
<div class="form-group col-md-8"><%= f.password_field(:password, :class => "form-control") %></div>
<div class="form-group">
<div class="form-group col-md-4"><%= f.label :confirmar_contraseña %></div>
<div class="form-group col-md-8"><%= f.password_field(:password_confirmation, :class => "form-control") %></div>
</div>
<div class="col-md-offset-2 col-md-10">
<button type="submit" class="btn btn-default">Cambiar Contraseña</button>
</div>
<% end %>