how to call javascript functions from the controller in rails

Question

I'm trying to call a javascript function (actually coffeescript) from a controller in a Rails 3.2 app.

I'm getting a Render and/or redirect were called multiple times in this action error.

My code looks like this:

#Model.controller

def index
  @models = Model.all
  my_action if current_user.name == "Bob" #or some other general conditional
  ...and some stuff
  respond_to do |format|
    format.html
    format.js #this is needed to handle ajaxified pagination
  end
end

def my_action
  respond_to do |format|
    format.js { render :js => "my_function();" } #this is the second time format.js has been called in this controller! 
  end
end


#functions.js.coffee.erb

window.my_function = ->
  i = xy
  return something_amazing

What is the correct way to call a js function from the controller?

I think in coffee you need to declare a function like my_function -> (check this: js2coffee.org and try your coffee script, it does not work) — MrYoshiji
– MrYoshiji, Commented May 22, 2013 at 17:00
I don't think my_function will be available as it isn't bound to the window or in the global namespace. See stackoverflow.com/questions/4214731/… and stackoverflow.com/questions/9059475/… — Shawn Balestracci
– Shawn Balestracci, Commented May 22, 2013 at 17:22

Billy Chan · Accepted Answer · 2013-05-23 03:40:29Z

14

Man, you missed argument for block. Primary mistake.

def my_action
  #respond_to do # This line should be
  respond_to do |format|
    format.js { render :js => "my_function();" }
  end
end

And MrYoshiji's point is right. But your error was on server side, had not reached client side yet.

For the style, I think that's okay if the js code is one function call only. If more JS code, it's better to render js template

 # controller
 format.js

 # app/views/my_controller/my_action.js.erb
 my_function();
 // and some more functions.

Update: How to fix double rendering problem

You must have your #index return if condition met, or the method will continue to execute and cause rendering twice or more. Fix it like this:

def index
  @models = Model.all
  if current_user.name == "Bob"
    return my_action
  else
    # ...and some stuff
    respond_to do |format|
      format.html
      format.js #this is needed to handle ajaxified pagination
  end
end

edited May 23, 2013 at 3:40

answered May 22, 2013 at 17:00

Billy Chan

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7 Comments

Andy Harvey Over a year ago

faceplant, good point. I've been playing with this too long! Problem not is that I have two blocks calling render (one in index, one in my-action) and this is throwing errors.

Andy Harvey Over a year ago

Thanks, this helps a lot and I think we're getting close to a solution. But I'm unable to resolve this Render and/or redirect were called multiple times errors. I've updated my question to provide more detail. Appreciate any ideas you may have

Andy Harvey Over a year ago

Thanks Billy, appreciate your quick response, and I apologize for maybe stupid questions while I try to understand this. I understand your solution above, but what if I want to add my_action to the functions already running on the page, not replace. For example, the javascript my_action function renders a popup only for Bob, but the rest of the page should still be rendered below this, not replaced. Thanks for helping me get to grips with this

Billy Chan Over a year ago

@AndyHarvey, I see your points. If you want to do this, controller action is not right solution. You can simply use template to do that: <% if current_user.name == "bob" %> <%= javascript_tag bla blah %>. This is much easier and makes sense.

Andy Harvey Over a year ago

hm yes, i thought of this but decided against it because it seems to go against the way javascript is handled in the asset pipeline, with all js loaded simultaneously. Perhaps I need to look at this again. So this is the way you would approach this? A js file that is not included in the application.js manifest, and a specific call to that js file in the view? It seems a bit clunky, surprised Rails doesn't have a "cleaner" way to handle this.

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