JSON data with ruby rails

My requirement is to fetch the JSON data from rails server and use it to update the place marks on a google map. I start with a view form that submits the user query. I am submitting this query form using the form_remote_tag

 

<%= form_remote_tag (:update =>; 'searchMapResults',:loading =>; "Element.show('spinner')",:complete =>; " Element.hide('spinner') ; ",
:id =>; 'searchMapForm' ,
:url =>; {:action =>; :searchMap}) %>;

Next, we go to the controller action that handles this request. searchMap action should fire a SQL query, load some data in instance variables and return part of data as JSON string to the UI. The controller action looks like

def searchMap
 # get the area and search token
 filter = params[:filter]
 binds = Hash.new 

 sql = { some sql ..... }
 @pmarks = Pmark.find_by_sql [sql, binds] payload = Hash.new
 points = Array.new

 @pmarks.each do |pmark|
 point = Hash.new
 point[:latitude] = pmark.latitude
 point[:longitude] = pmark.longitude
 point[:name] = pmark.name

 point[:description] = pmark.description 
 points.push(point)
 end
 payload[:markers] = points 
 @jsonData = payload.to_json
 logger.debug( " gloo : markers json data" + @jsonData);
 render(:layout => false )

end

We fire a SQL query and load the results. Next we create a Hash (payload) of arrays (markers) of hash (point). we convert this payload RUBY data structure to JSON string using the Active support JSON gem. I installed this gem using command


$gem install json

This gem provides a ready made to_json method. Next step is to use this JSON data string inside our view and javascript files. Our searchMap.html (view for this action looks like:)

 


<script>
loadPoints('<%= @jsonData %>');
</script>

And finally inside a loadPoints javascript function we evaluate the JSON data and use it.

 

function loadPoints(content){
 var jsonData = eval('(' + content + ')');
  for (var i=0; i<>
   alert(jsonData.markers[i].name);

  }
 }