Working with Rails arrays in Postgres

Question

I have a postgres column called content which is an array.

But when trying to use it in a form I'm getting:

can't cast ActionController::Parameters to text

Despite the fact that the output looks pretty good:

{"utf8"=>"✓",
 "_method"=>"patch",
 "authenticity_token"=>"NkK4BggxknfEn0A8shTs06xmesERaZdYtZdl9oEEUTk=",
 "notification_template"=>{"content"=>{"0"=>"Join us {{event_time}} {{{twitter_name}}} to win Big! hint: {{{question}}} #quiz {{location_tags}} {{url}} sdfsdfsdf"}},
 "commit"=>"Update Notification template",
 "id"=>"25"}

strong params

params.require(:notification_template).permit(:name, :content => {})

routes

resources :notification_templates do
  get 'edit/:id', to: 'notification_templates#edit_content', as: 'edit_content'
end

controller

  def edit_content
    @notification_template = NotificationTemplate.find(params[:notification_template_id])
  end

  def update
    if @notification_template.update(notification_template_params)
      redirect_to admin_notification_template_path(@notification_template), notice: 'Social message was successfully updated.'
    else
      render action: 'edit'
    end
  end

my form

the url looks like: /notification_templates/25/edit_content/7 # custom action, but uses normal update

<%= simple_form_for([:admin, @notification_template]) do |f| %>
  <%= f.error_notification %>

  <div class="form-inputs">
    <%= f.simple_fields_for :content do |fields| %>
        <%= fields.input params[:id], input_html: { value: @notification_template.content[params[:id].to_i] } %>
    <% end %>
  </div>

  <div class="form-actions">
    <%= f.button :submit %>
  </div>

<% end %>

the DB column

add_column :notification_templates, :content, :text, array: true, default: []

Lastly, I was unsure about the conventions for adding it. The above worked fine, but I also noticed other possibilities such as

add_column :notification_templates, :content, :text, array: true, default: []
add_column :notification_templates, :content, :sting, array: true, default: []
add_column :notification_templates, :content, :text, array: true, default: {}

I choose the first one on the basis that a string wouldn't allow for as many characters as I might eventually need and text is more convenient. Also the default of [] vs {} or '{}'

But in postgres is see content text[] DEFAULT '{}'::text[]

log

Started PATCH "/admin/notification_templates/25" for 127.0.0.1 at 2014-11-28 14:25:43 +0100
Processing by Admin::NotificationTemplatesController#update as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"NkK4BggxknfEn0A8shTs06xmesERaZdYtZdl9oEEUTk=", "notification_template"=>{"content"=>{"4"=>"{{{question}}} Study up and stop by {{{twitter_name}}} {{event_time}} for a #quiz {{location_tags}} {{url}} sdfsdfsdf"}}, "commit"=>"Update Notification template", "id"=>"25"}
  User Load (0.9ms)  SELECT  "users".* FROM "users"  WHERE "users"."id" = 1  ORDER BY "users"."id" ASC LIMIT 1
  NotificationTemplate Load (0.5ms)  SELECT  "notification_templates".* FROM "notification_templates"  WHERE "notification_templates"."id" = $1 LIMIT 1  [["id", 25]]
   (0.3ms)  BEGIN
   (0.3ms)  ROLLBACK
Completed 500 Internal Server Error in 54ms
Reporting exception: can't cast ActionController::Parameters to text

TypeError (can't cast ActionController::Parameters to text):
  app/controllers/admin/notification_templates_controller.rb:40:in `update'


  Rendered /Users/holden/.rvm/gems/[email protected]/gems/actionpack-4.1.7/lib/action_dispatch/middleware/templates/rescues/_source.erb (1.1ms)
  Rendered /Users/holden/.rvm/gems/[email protected]/gems/actionpack-4.1.7/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb (2.0ms)
  Rendered /Users/holden/.rvm/gems/[email protected]/gems/actionpack-4.1.7/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb (1.4ms)
  Rendered /Users/holden/.rvm/gems/[email protected]/gems/actionpack-4.1.7/lib/action_dispatch/middleware/templates/rescues/diagnostics.erb within rescues/layout (27.5ms)

UPDATE

I also observed that update array type field doesn't work as expected in the console.

eg. if I attempt to update a member of the array, something = record.content[2] = 'blah' it appears to work. But when I save the record it doesn't update it.

Answer 1

Yeah, Rails postgres Arrays are still a bit wonky. Hstore is a bit easier.

You may be better served going thru a virtual attribute and doing what you want expressly rather than relying on standard rails behavior through a form.

eg.

def content_member=(member)
    unless member.blank?
        self.content_will_change!
        self.content[member.keys.first.to_i] = member.values.first
    end
end

You also need to let rails know if you're going to update a member of an array, that's why it doesn't work in the console.

There's a full explanation here:

Rails 4 Postgresql array data-type: updating values