Rails - Oct 2011 - How to access controller's instance variable in a js.erb loaded by javascript_include_tag?

Hello!

In rails 3.1 app I have a controller UsersController with
''show'' action.
show.html.erb contains:

<% content_for(:head) do %>
<%= javascript_include_tag ''myscript'' %>
<% end %>
<p>Hello @user.name</p>

And I have this in myscript.js.erb

$jQuery(document).ready(function() {
alert(<%= @user.name %>);
});

@user is being assigned by a controller and it works just ok in 
show.html.erb, but in myscript.js.erb I get nil as @user and exception is 
thrown.

What''s my error here? How to get around this? 
I googled, but all suggestions I found were about rendering partial and 
using :local option to pass a variable to it.
Is this the only option?
I''m asking because I suspect I miss something. It would look really
natural
for @user being accessible in js.erb loaded through 
javascript_include_tag...

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You render the value in the template and grab it via javascript, like this:



<%= tag :meta, :name=> ''user_name'', :content=>
@user.name%>


$(''meta[name=user_name]'').attr(''content'');

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And what if it is a large array of values?...
Ok to pass them as a contents of the tag?
I know I could do it with ajax request, but how do I pass this large amount 
of data when JS is disabled...
What I''m doing is feeding data to jQuery Flot library.
And it accepts data in place of a plot initialization, e.g.

$.plot("#placeholder", data)

so I need to somehow inline this data when initializing element => js.erb.
And then I expect to have something like:

$.plot("#placeholder", <%= @user.generate_flot_data %>)

I''m a bit new to this stuff, may ask stupid questions :)

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On Oct 12, 9:19 pm, Dmitry Suzdalev
<dim...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> Hello!
>
> In rails 3.1 app I have a controller UsersController with
''show'' action.
> show.html.erb contains:
>
> <% content_for(:head) do %>
> <%= javascript_include_tag ''myscript'' %>
> <% end %>
> <p>Hello @user.name</p>
>
> And I have this in myscript.js.erb
>
> $jQuery(document).ready(function() {
> alert(<%= @user.name %>);
>
> });
>
> @user is being assigned by a controller and it works just ok in
> show.html.erb, but in myscript.js.erb I get nil as @user and exception is
> thrown.
>
> What''s my error here? How to get around this?
> I googled, but all suggestions I found were about rendering partial and
> using :local option to pass a variable to it.
> Is this the only option?
> I''m asking because I suspect I miss something. It would look
really natural
> for @user being accessible in js.erb loaded through
> javascript_include_tag...
javascript_include_tag generates a <script> tag in the output. When
the browser renders your page, it looks at that script tag and
requests myscript.js from your server. By now, the original controller
and its @user variable are long gone, you''re instead looking at the
@user from a new controller, which is apparently null. one way of
dealing this might be

<% content_for :head do %>
<%= javascript_tag "var js_user_name = #{@user.name.to_json};"
<%= javascript_include_tag ''my script'' %>

<% end %>

which creates a (javascript) variable called js_user_name that your
javascript would be able to use. Another option would be to pass
information about which user to pick via a query parameter (i.e.
instead of the url requested being /javascripts/myscript.js it would
be /javascripts/myscript.js?user_id=123), and have the controller that
renders the javascript set up @user accordingly.

Fred

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Thank you very much, Frederick, very useful!
I think I will go on with the first method (for starters)! :-)

Cheers,
Dmitry.

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