How to call rails method from view on button or link click

Question

Basically, I'm trying to have a rails method execute when the user clicks on a link (or a button or some type of interactive element).

I tried putting this in the view:

<%= link_to_function 'Add' , function()%>

But that didn't seem to work. It ended up simply calling the function without a user even clicking on the "Add" link.

I tried it with link_to as well, but that didn't work either. I'm starting to think there isn't a clean way to do this. Anyway, thanks for your help.

PS. I defined the method in the ApplicationController and it is a helper method.

Solution

The view and the controller are independent of each other. In order to make a link execute a function call within the controller, you need to do an ajax call to an endpoint in the application. The route should call the ruby method and return a response to the ajax call's callback, which you can then interpret the response.

As an example, in your view:

<%= link_to 'Add', '#', :onclick => 'sum_fn()' %>
<%= javascript_tag do %>
    function sum_fn() {
        /* Assuming you have jQuery */
        $.post('/ajax/sum.json', {
             num1: 100,
             num2: 50
        }, function(data) {
             var output = data.result;
             /* output should be 150 if successful */
        });
    }
<% end %>

In your routes.rb add a POST route for your ajax call endpoint.

post '/ajax/sum' => 'MyController#ajax_sum'

Then suppose you have a MyController class in mycontroller.rb. Then define the method ajax_sum.

class MyController < ApplicationController
    # POST /ajax/sum
    def ajax_sum
        num1 = params["num1"].to_i
        num2 = params["num2"].to_i
        # Do something with input parameter and respond as JSON with the output
        result = num1 + num2

        respond_to do |format|
              format.json {render :json => {:result => result}}
        end
    end
end

Hope that hopes!

Comments

[sealocal]

I think you have to use parens to call the function: :onclick => 'sum_fn()'. Right?

[Bobby]

Fixed thanks! Using onclick is probably not the best way of registering a click handler. It should instead be registered with Javascript, but for the purposes of demonstration, I think this is enough.

[Justin Harris]

Thanks but you're missing a closing bracket on the post function.