Retrieving Controller Data in AJAX Response with Rails 5

After researching numerous articles on this topic, I find myself more confused than enlightened. The various approaches to the same task in Rails have left me feeling overwhelmed.

The traditional method of handling AJAX calls involves:

  1. JavaScript listening for a specific event.
  2. When the event occurs (e.g., a button click), JavaScript initiates an AJAX call, and the success or error response is managed within that call.

However, attempting to implement this in Rails 5 presents challenges, particularly when it comes to passing data from the controller to JavaScript.

Within the controller:

class SomeController < ApplicationController
  def show
  end

  def foo
    @result = 'Hello World'
    respond_to do |format|
      format.js {@result}
    end
  end

In the view, I have a form with remote: true, which triggers an AJAX request to the 'foo' action in the controller:

=form_tag url_for(action: 'foo'), remote: true, id: 'element-form' do
  =some input ....
  =some input ...

For the JavaScript in foo.js.erb located in /views/some/foo.js.erb:

$('#element-form').on ('ajax:complete', doSomething)

function doSomething(event, data) {
  console.log(data) // prints undefined
}

$('#element-form').on ('ajax:error', doSomethingElse)

function doSomethingElse(event, data) {
  console.log(data) // prints undefined
}
  1. I am struggling with accessing the data from the controller in the AJAX onsuccess function. What might I be doing wrong?
  2. I feel uneasy about using the *.js.erb file as it seems to blend views and JavaScript. Is there a better way to handle AJAX calls in Rails without relying on *.js.erb?
  3. Is there a way to pass controller data to JavaScript files for handling AJAX responses without using *.js.erb?
  4. How can I define separate success and error handlers for AJAX responses in Rails without resorting to manual code declarations?

When inspecting the AJAX call in the browser, I receive a valid response containing the JavaScript defined in the foo.js.erb file.

My primary issue lies not in specific code snippets but in grasping the interconnection of all components. I struggle to comprehend the data flow and request response cycle involved in making AJAX requests within a Rails 5 environment. Any recommended resources on this subject would be greatly appreciated.

Answer №1

After many trials, I finally mastered the art of handling ajax requests and responses. Here's the breakdown of how I made it work seamlessly.

Keeping the controller logic intact, I decided to fine-tune the ajax request by adding the necessary logic in the some_controller.js file. As Sergio mentioned in one of his comments, it seemed futile to introduce callback methods in the *.js.erb file at a later stage.

The javascript code snippet I implemented is as follows:

$(document).ready(function() {
  $('#some_element').on('some_event', function doSomething() {
    makeAjaxCall();
  });

  function makeAjaxCall() {
    Rails.ajax({
        type: "POST",
        data: {mock_data: mock_data},
        url: 'post_url',
        success: function(response){...},
        error: function(error){...}
      });
  }
});

The crucial part lies in the response after the post method in the rails controller (action) is executed. Rails expects a corresponding view to render, preferably a js view with the same name as the action method (action_method.js.erb).

To send controller data to the ajax callback blocks effortlessly, simply include it in this js view. In my scenario, the JavaScript: foo.js.erb in /views/some/foo.js.erb was modified to:

<%=@result %>

Upon completion, the control shifts back to the client-side javascript, specifically the ajax success callback method. Whatever content is placed in the *.js.erb file is readily accessible in the response.

Answer №2

foo.js.erb functions as an ERB view, just like any other. Therefore, you can access your controller data in the usual way.

 console.log("<%= @result %>");

(there is no need to include ajax:complete in the .js.erb file, by the way)

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