jQuery post to Rails

Question

My setup: Rails 3.0.9, Ruby 1.9.2, jQuery 1.6.2

I have a form that shows multiple photos and comments for a user and I wish to implement inline commenting.

<div id="newsfeed">    
 <div> 
 <div class="photo_title">Summer 2011</div> 
 <div class="newsfeed_photo"> 
 <a href="..." /></a> 
 </div> 
 <textarea class="comment_box">Write a comment...</textarea>  
</div> 
<div> 
 <div class="comment_title">Seeing a movie</div> 
 <textarea class="comment_box">Write a comment...</textarea>  
</div> 

I want to submit an AJAX post upon the user hitting the enter key in the textarea field. Here's the javascript (incomplete) that I have so far

  $('#newsfeed').delegate('.comment_box', 'keydown', function (event){
    event.preventDefault();
    $.post('/sub_comments', ...);
  });

I'm using the delegate method because <div id='newsfeed'> contents could be replaced with another AJAX call. What I need is the syntax for jQuery post method assuming I need to pass some form params like say photo_id, etc. Assume that I have a way to access the values for the params, what's the syntax for the post call to creating params the way Rails expect them

Here's the standard Rails bits

sub_comments_controller.rb

  def new
    @sub_comment = SubComment.new

    respond_to do |format|
      format.html # new.html.erb
      format.js
    end
  end

Also I don't want to use the usual <%= form_for(@sub_comment, :remote => true) do |f| %> for each and every inline comment I could add. I have also taken a look at Ryan Bates's railscast but the code looks outdated.

Solution

You can setup your post to structure the data in any way as long as it is interpreted correctly on the rails end, but best practice is to have an object of 'model-name' with all the values.

Javascript

$.ajax({
    url: "/sub_comments",
    type: "POST",
    data: {subcomment: {
             field: val, 
             field2: val, etc... }},
    success: function(resp){ }
});

Rails

def create
  @sub_comment = SubComment.new params['subcomment']
  if @sub_comment.save
    render :json => { } # send back any data if necessary
  else
    render :json => { }, :status => 500
  end
end

Comments

[Mario Zigliotto]

would you mind explaining why you chose to not use a respond_to block please? thank you!

[DonPaulie]

@MarioZigliotto He did it only because it is shorter to write. The consequences are that he cannot render html in this action, only json.

[developer01]

@DonPaulie is it not possible to render JSON in an html.erb view? I know this answer is really old. I'm using Rails 6.

[DonPaulie]

@developer01 I am not sure if I understand your question. If you want multiple formats, definitely use respond_to with block. If you want to build the json in some kind of view file (and not in controller), you can simply name the file create.json.erb and write the contents. But then I would recommend you jbuilder gem or some serializer pattern.