CODEWITHSUNDEEP
jqueryruby-on-rails
muichkine
muichkine

Reputation: 2940

rails renders invalid json

I have a strange behavior where an ajax query fails parsing a JSON object returned by my rails 4.1.4 server (jquery-rails is 3.1.1). Yet, the controller is dead stupid:

class WelcomeController < ApplicationController    
  def create
    respond_to do |format|
      format.json{ render json: 'ok' }
    end
  end   
end

and the Ajax query is all very standard (CoffeeScript):

window.Api = {}

(->
  queryFx = (dataType, type, url, data, successFx, failureFx) ->
    $.ajax
      url: url
      type: type
      dataType: dataType
      beforeSend: (xhr) ->
        xhr.setRequestHeader('X-CSRF-Token', $('meta[name="csrf-token"]').attr('content'))
      success: (json) ->
        console.log(json)
      error: (xhr, status, errorThrown) ->
        console.log(status, errorThrown)

  Api.post = (url) ->
    queryFx('json', 'POST', url)

)()

$(document).ready( ->
  $('#request').submit( (event) ->
    event.preventDefault
    window.Api.post($(this).attr('action'))
    return false #Prevent the normal submission
  )
)

the query goes fine, only when the reply comes, ajax throws:

"parsererror" SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data
Stack trace:
jQuery.parseJSON@http://localhost:3000/assets/jquery.js?body=1:8483:3
ajaxConvert@http://localhost:3000/assets/jquery.js?body=1:8809:8
done@http://localhost:3000/assets/jquery.js?body=1:9226:4
.send/callback@http://localhost:3000/assets/jquery.js?body=1:9686:8

Is there anything to do on the rails server so it outputs proper JSON for jquery?

Upvotes: 0

Views: 991

Answers (2)

Anton G
Anton G

Reputation: 129

I've just faced the similar problem. I also advise you to check your ajax response string for invalid format first before using it as a json object. I'm not familiar with coffeescript, that's why I give you a native js sample. So try to put the following code into your AJAX complete callback function:

    complete: function(data) {
        var jsonRes = null;
        try {
            jsonRes = JSON.parse(data.responseText);
        }
        catch(e) {
            jAlert('Invalid JSON object);
        }
        if (jsonRes===null || jsonRes.result===undefined) {
            jAlert('Invalid Ajax response structure');
        }
    }

Upvotes: 0

Marc-Alexandre B&#233;rub&#233;
Marc-Alexandre B&#233;rub&#233;

Reputation: 2171

Your controller is dead stupid but does in fact render invalid json ;) You should pass an Hash to the json option of render. Try it like this :

class WelcomeController < ApplicationController    
  def create
    respond_to do |format|
      format.json{ render json: { ok: 'ok' } }
    end
  end   
end

Upvotes: 4

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