At least one entry for DB

rubyonrails-talk
1

Rails 3.1.3

I have models and their association like,

Video 1: -------- n: Script

When users newly create a Video, I want it to create the very first Script entry together.

I have put

    @script = Script.new(:video_id => @video.id, :startp => 0, :text => 'ToDo: ')

in Video controller, 'new' action, but it doesn't work (:startp value is determined for the first one).

How can I create a Script entity together with Video?

Also, if possible, I want that first Script entry to be undestroyable. Do you think I can do it?

Thanks in advance,

soichi

2

You can use either an after_create on the model or an observer which observes a Video creation.

Personally, I usually prefer observers which seem less intrusive to me, giving a better to make it active or unactive, but some people think the other way.

To make your first script undestroyable, you can add a column to the model or a ‘before_destroy’ which checks if its the first Script created for a given Video, a method to check this same condition and hide ‘destroy’ links… there is a lot of ways to do this.

3

Thanks for your answer.

I will try after_create.

I have put

  after_create :create_first_script

  def create_first_script     @video = Video.new(params[:video])     @script = Script.new(:video_id => @video.id, :startp => 0, :text => 'ToDo: ')   end

in video.rb. But I need to pass params[:video] somehow...

/videos/_form.html.erb (generated by scaffold) should do it, correct?

<%= form_for(@video) do |f| %>

  <div class="field">     <%= f.label :title %><br />     <%= f.text_field :title %>   </div>   <div class="field">     <%= f.label :url %><br />     <%= f.text_field :url %>   </div>   <div class="actions">     <%= f.submit %>   </div> <% end %>

I am not sure how to pass the video object from here. Could anyone give me tips?

soichi

4

Hey,

The @video.id you are referring to is not yet existing as the @video object is not yet persisted into the db.

You have to first save the @video before accessing the id, that is when the after_create or after_save is triggered.

In your Video class, the after save has access to the @video instance through the self keyword (self.id in your case).

Another solution to your problem would be to use nested attributes (see accepts_nested_attributes_for in the rails docs)

I hope this helps.

Regards

Geoffroy

5

Thanks for you answer.

You have to first save the @video before accessing the id, that is when the after_create or after_save is triggered. In your Video class, the after save has access to the @video instance through the self keyword (self.id in your case).

I need to clarify this point.

When videos_controller.rb calls for 'create' action, a new instance gets persisted, correct? When doing so, 'after_create' is called as well. It seems to me that when 'after_create' is called, the new video instance is already created. Please correct me, if I'm wrong.

I tried this. but no good ( I knew it! )

  after_create :create_first_script

  def create_first_script     @script = Script.new(:video_id => self.id, :startp => 0, :text => 'ToDo: ')   end

soichi

6

Thanks for you answer.

You have to first save the @video before accessing the id, that is when the after_create or after_save is triggered. In your Video class, the after save has access to the @video instance through the self keyword (self.id in your case).

I need to clarify this point.

When videos_controller.rb calls for 'create' action, a new instance gets persisted, correct? When doing so, 'after_create' is called as well. It seems to me that when 'after_create' is called, the new video instance is already created. Please correct me, if I'm wrong.

Calling the create action in the controller does not create it in the database, it is the call of 'save' within the create action that saves it to the database. The after_save callback will be called from within save, after it is saved to the db and then the id will be valid.

I tried this. but no good ( I knew it! )

after_create :create_first_script

def create_first_script @script = Script.new(:video_id => self.id, :startp => 0, :text => 'ToDo: ') end

What do you think that code does? It creates a new object in memory, but you have not saved it to the database, so after the method is called your new object is immediately lost.

Colin

7

Indeed, you should save (persist) your object (script) after creating it or use the create (or create!) method instead or new:

@script = Script.new(:video_id => self.id, :startp => 0, :text => 'ToDo: ')

@scipt.save

or

@script = Script.create(:video_id => self.id, :startp => 0, :text => 'ToDo: ')

regards

Geoffroy

8

But something like

@video = Video.new({…})

@script = @video.scripts.build({ :startp => 0, :text => 'ToDo: '}) @video.save

doesn’t work?

9

Thanks! Finally I got it done.

  after_save :create_first_script

  private   def create_first_script     @script = Script.new(:video_id => self.id, :startp => 0, :text => 'ToDo: ')     @script.save   end

soichi