Dynamic build JSON variable from HTML5 mobile send to Ruby on Rails controller

Client: HTML5 + JS + localdb Server: Rails3

I'm trying to code small mobile app: the app if a small form that records some contacts info into a local database. Then when clicking on a Sync button it send the contacts to a RoR app.

Trying to follow some best practise I would like to store the data on JSON format before sending it to the RoR app. The JSON variable is building dynamically from a localdb:

on client side:

var myJSON= { 
            jcontacts:[]
        }; 

...
// loop on localdb
for (var i=0; i< vContacts.length;i++)
{                               
    myJSON.jcontacts.push({
        "name"      : vContacts[i][0],
        "email"     : vContacts[i][1],
        "info"      : vContacts[i][2]
    });                                                                                     
}           
var myJSONText = JSON.stringify(myJSON);    //(1) convert array to JSON string                                              

/*
console.log(myJSONText) --> {"jcontacts":[{"name":"John","email":"john@email.com","info":"Owner"},
{"name":"Mary","email":"mary@gmail.com","info":"Doctor"},
{"name":"Gary","email":"gary@email.com","info":"Driver"}]}
*/

var myObject = JSON.parse(myJSONText);// (2) convert JSON string to JSON object, just do it to make sure my var is valid JSON format
myGlobalJSONText = JSON.stringify(myObject); // (3) convert JSON object to JSON string before sending to server

/*
console.log(myGlobalJSONText) --> {"jcontacts":[{"name":"John","email":"john@email.com","insurance":"Medical"},
{"name":"Mary","email":"mary@gmail.com","insurance":"Medical"},
{"name":"Gary","email":"gary@email.com","insurance":"Car"}]}
*/
...
// Ajax
   $.ajax({
        type: "POST",                    
        url : "http://localhost:3000/contacts/multinew",
        cache: false,
        data: myGlobalJSONText,
        success: onSuccess,
        error: onError
    });

On Rails side:

def multinew        
    @vcontacts = JSON.parse(params[:jcontacts])     
    @vcontacts.each {|x| Contact.create(x)}   

    respond_to do |format|
        format.html { redirect_to(@contact)}
      format.xml  { head :ok }
    end
 end

When sending the data, my Rails server replies:

Started POST "/contacts/multinew" for 127.0.0.1 at 2011-04-25 20:49:23 +0700
  Processing by ContactsController#multinew as */*
  Parameters: {"{\"jcontacts\":"=>{"{\"name\":\"John\",\"email\":\"john@email.com\",\"info\":\"Owner\"},{\"name\":\"Mary\",\"email\":\"mary@gmail.com\",\"info\":\"Doctor\"},{\"name\":\"Gary\",\"email\":\"gary@email.com\",\"info\":\"Driver\"}"=>{"}"=>nil}}}
Completed   in 0ms

TypeError (can't convert nil into String):

So my questions are:

1) before trying to fix the Rails part I would like to know if everything is correct on the client javascript code? My assumption using JSON is that if a variable is properly formed on client side (using JSON.stringify) it should be interpreted correctly on server side (using JSON.parse), this is the reason why people use JSON?

2开发者_StackOverflow社区) if the client code side is correct it means I should fixe the ruby code by putting some regex processing? Is this case I cannot see the advantage of using JSON (others the security reason)

Many thanks!

I finally come with this solution:

1/ On client side, I send a JSON object not a JSON stringified variable

2/ On Server side I made a small fixe to transform the has_array variable received to a simple array

ANY BETTER SUGGESTION IS WELCOME!

Client:

{                               
    myJSON.jcontacts.push({
        "name"      : vContacts[i][0],
        "email"     : vContacts[i][1],
        "info"          : vContacts[i][2]
    });                                                                                     
}                                                                   

myJSONText = JSON.stringify(myJSON);    // array to JSON string , I cannot avoid this step before calling the PARSE method hereafter                                                                        
myGlobalJSONText = JSON.parse(myJSONText); // JSON string to JSON object    

Server: The variable is received as an hash_array of has_array elements

{"0"=>{"name"=>"John", "email"=>"john@email.com", "info"=>"Doctor"},
"1"=>{"name"=>"Mary", "email"=>"mary@gmail.com", "info"=>"Driver"},
"2"=>{"name"=>"Gary", "email"=>"gary@email.com", "info"=>"Owner"}}

but we should transform it to an array of has_array elements:

[{"name"=>"John", "email"=>"john@email.com", "info"=>"Doctor"},
 {"name"=>"Mary", "email"=>"mary@gmail.com", "info"=>"Driver"},
{"name"=>"Gary", "email"=>"gary@email.com", "info"=>"Owner"}]

To do so:

def multinew            

@hash_contacts = params[:jcontacts]         
@array_contacts = Array.new
@hash_contacts.each_value {|value| @array_contacts<<value }

@array_contacts.each {|x| Contact.create(x)}   

...