{ StevenHaddox.com }

I’m developing an application that needs to have a normal web presence (typical HTTP/HTTPS) as well as a very easily consumable 3rd party API. With these requirements in mind I easily decided to run with Ruby on Rails (.to_json anyone?) I’ve been working on it for over a month now and have encountered a situation where my controllers are getting a little large due to having to handle logic on whether the request via the API url was a Javascript AJAX requests or a regular HTTP request. Generally this is easily solved in the respond to block with something like:

respond_to do |format|
  format.html # reports/show.rhtml
  format.js { render :partial => 'reports/show' } # reports/_show.rhtml
end

This example is just rendering a partial that is also used in my show.rhtml to save updating more than one file at a time. However, my current project started turning into things like this (due to the API methodology we had decided upon with the client in advance that got extended into doing things we hadn’t anticipated):

# show method
respond_to do |format|
  format.html # reports/show.rhtml
  format.json { render :json => @report } # json format of the report data
  format.js { render :partial => 'reports/show' } # reports/_show.rhtml
  format.js_vdata {
    render :template => 'reports/show.visual_json', :layout => false, :content_type => 'application/json'
  }
  format.table {
    render :template => 'reports/show.html_table', :layout => false, :content_type => 'application/json'
  }
  ... [more formats for special MIME types here with customized views all from the same report data] ...
end

As you can see this code was being extended to generate multiple kinds of reports for loading via an API with AJAX requests. The extra formats are all being returned as JSON in order to allow for JSONP and remote-access from other domains and then the user can display the requested data / customize it as they desire. But how did I go about providing those same views to users on the web application itself? Create another format just to render the same view for regular HTTP requests? Definitely not very DRY. So it occurred to me that the following might be a possible solution:

#Controller show method
respond_to do |format|
  ...
  format.js_vdata {
    if request.xhr?
      render :template => 'reports/show.visual_json', :layout => false, :content_type => 'application/json' and return
    else
      render :template => 'reports/show.visual_json', :layout => true, :content_type => 'text/html' and return
    end
  }
  format.table {
    if request.xhr?
      render :template => 'reports/show.html_table', :layout => false, :content_type => 'application/json' and return
    else
      render :template => 'reports/show.html_table', :layout => true, :content_type => 'text/html' and return
    end
  }
end

#View template for reports/show.visual_json
< %- if request.xhr? -%>
  < %= @report.visual_data.to_json %>
< %- else -%>
  
  < %=debug @report.visual_data %>
< %- end -%>

Although this was a basic proof of concept there was already a problem with it. Any request coming from a remote domain would send requests for ‘jsonp’ and would not be recognized by request.xhr? (at least with jQuery 1.2.6 on the server we were consuming this API). I’m not sure why this was, but it seemed to be the situation I had to work with. This meant those requests were getting the HTML version of the page (not fun for parsing via Javascript). The solution I found was this (please note this is a very initial stab and is more than open to refactoring suggestions):

#Controller
before_filter :set_request_type

#show method
respond_to do |format|
  ...
  format.js_vdata {
    begin
      render_dynamic_template('reports/show.visual_json')
    else
      render_dynamic_template('reports/show.nil')
    end
  }
  format.table {
    begin
      render_dynamic_template('reports/show.html_table')
    else
      render_dynamic_template('reports/show.nil')
    end
  }
end

private
  def set_request_type
    @ajax_request = true if request.xhr? or (params[:callback] && params[:callback].include?('jsonp'))
  end

  def render_dynamic_template(template)
    template = 'reports/show.nil' if template.nil?
    if @ajax_request
      layout = false
      content_type = 'application/json'
    else
      layout = true
      content_type = 'text/html'
    end
    render :template => template, :layout => layout, :content_type => content_type
  end

#View template for reports/show.visual_json
< %- if @ajax_request -%>
  < %= @report.visual_data.to_json %>
< %- else -%>
  
  < %=debug @report.visual_data %>
< %- end -%>

#View template for reports/show.nil
< %- if @ajax_request -%>
  < %= [nil].to_json %>
< %- else -%>
  
  < %= 'There is no data at this time.' %>
< %- end -%>

Also, the best tutorial I could find for implementing jsonp support with a quick (like 2 minute) Google search was over at Sitepoint

And that should allow you to render both html and json/jsonp results based upon the kind of request coming in. Obviously it makes an assumption that remote jsonp requests will provide a parameter of ‘callback’ that includes ‘jsonp’ in the string, but given that it is your API that’s not a huge requirement to impose and you can customize it to how you see fit.

If you know of a better way to go about approaching this kind of task I’m more than open to being educated, but given the short time-frame I had and the few tutorials specific to jsonp I found this to be a pretty good first stab. Hopefully this post will help someone else if they find themselves looking for some way to accomplish similar tasks.

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