Question

I’m getting a double render error that I cannot get rid of in the update method of my model.

Here’s the code for the controller

class Admin::CmsHappeningNowFeatureController < ApplicationController

    def index
        # Various model data retrieval...

        render 'admin/cms/hn_features/index', layout: 'admin_cms'
    end

    # Works fine
    def edit
        @feature = CmsHappeningNowFeature.find_by_id(params[:id])
        render 'admin/cms/hn_features/feature', layout: 'admin_cms'
    end

    # Throws a AbstractController::DoubleRenderError upon submission
    def update
        @feature = CmsHappeningNowFeature.find_by_id(params[:id])
        @feature.attributes = params[:cms_happening_now_feature]
        if @feature.save
            redirect_to(:action => index, :notice => "Successfully updated feature.") and return
        end 
        render 'admin/cms/hn_features/feature', layout: 'admin_cms'
    end

    # ... rest of the class
end

When redirecting to another controller, the issue disappears. It seems that redirecting to the same controller makes rails execute the method without actually sending a redirect. By looking at the log, when submitting the update form, update gets called, then index gets called, render from index is executed and then the redirect is issued and fails.

What am I missing? What’s the workaround?

Answer 1

Okay, the real cause is that in

redirect_to(:action => index, :notice => "Successfully updated feature.") and return
#                      ^^^^^ This calls the index method

you call the index method which will then render first. The redirect_to call will then get the result of that function back (which will be whatever the rendercall in index returns). and renders the second time

What you really want to write is this:

redirect_to(:action => :index, :notice => "Successfully updated feature.") and return

where you set :action to a symbol, i.e. index which represents the action but does not directly call it.