Rails Rendering a partial within JSON - ruby-on-rails

Question

I am trying to render a partial inside a JSON file so that I can use it via AJAX. Currently in my JSON file I have:
<% self.formats = ["html"]%>
{
"html": "<%= raw escape_javascript(render(:partial => 'shared/mini_posts', :locals => {:type => "left"}).to_json )%>"
}
This currently returns no response, but my logs show that shared/mini_posts was rendered.
Note that if I try something like:
{
"html" : "test"
}
This returns correctly.
My jQuery looks like:
$j.ajax({
url('/thepage.json'),
dataType: 'json',
success: function(data){
console.log(data);
}
})

Answer 1

In my case, I had the same problem for about a day and a half and after trying lots of combinations of escape_javascript, to_json, render ... content_type, etc I finally achieved what I was looking for, that is rendering a HTML partial in a json response.
So in your controller you have an action like
def index
#candidatos = Candidatos::Base.paginate(page: params[:page], per_page: 3).to_a
respond_to do |format|
format.html # index.html.erb
format.json # index.json.erb
end
end
and if the request had a .json it will use the index.json.erb template, and in my case that template is something like
<% self.formats = ["html"] %>
{
"html":<%= thumbnails_tag(#candidatos).to_json.html_safe %>
}
Note the self.formats = ["html"] is necessary because otherwise the "view" won't find the partial because it will look for a .json partial. and more important, don't use escape_javascript because it will fill the html with \t and \n. In other words, the idea is to pass the output of your partial to .to_json and then to .html_safe.
thumbnails_tag is just a helper I created because I'm using the partial in lots of parts of the app, but basically it has something like
def thumbnails_tag objs
#Uncomment the line below to test when no much data available
# #listas.fill(#listas.first, 0..6)
thumb_span = 4
case #candidatos.length
when 1..3
thumb_span = 12 / #candidatos.length
else
thumb_span = 4
end
thumbs = {span: thumb_span}
render partial: 'candidatos/thumbnails', locals: {candidatos: #candidatos, thumbnail_options: thumbs }
end
Finally, and just as an example, with this approach, in your .js assets you can do something like:
$.get('http://localhost:3000/candidatos.json?page=2', function(d){}, 'json')
.success(function(d){
$('#presidentes div.row-fluid .thumbnails').parent().append(d.html);
})
.error(function(event,error){
console.log(error);
})
No need to gsub for \t and \n in your rails view or JSON.parse string in your Javascript.

Answer 2

You need to change your controller. In the respond_to part you need to add json rendering. Like this:
respond_to do |format|
format.json { render :json => #instancevar }
....
...
..
end
Then you can simply add .json to your url and you will receive the data formated as json. What you might need to do is disabeling the JSON root hich is automaticly added by default. Just add this line to your environment (development.rb, production.rb,...) configuration:
config.active_record.include_root_in_json = false
This is important when you are parsing the json.

Answer 3

You can't call to_json on a partial... it's a method of ActiveRecord. If you want json there, then it should be inside the partial.