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davidn...@gmail.com

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May 29, 2007, 8:10:29 AM5/29/07
to Ruby on Rails: Talk
I saw this older post when searching for information:

On Feb 16, 5:10 pm, Ingo Weiss <rails-mailing-l...@andreas-s.net>
wrote:

> withfragmentcachingonecancacheparts of a page. However, more often
> than not what I would need is the exact opposite approach. I would like
> to be able to use action cashing and have a mechanism for telling Rails
> to excludeoneor more areas from the cashing and fill them with dynamic
> content instead. A good example would be a page whereallcontent would
> be perfectly cachablebutonetiny line saying 'logged in as
> [username]'.
>
> Wouldn't a mechanism for doing this more elegantly be a great addition
> to Rails? Or am I missing something and this is in fact currently
> possible?

I have exactly the same need - a front page that has a bit of text
that changes depending on whether the user is logged in or not.
Everything else could be cached using page cacheing.

Hrm.... I'll take a look at the code... maybe something like
'cache_except' is possible?

Thanks,
Dave
--
http://www.dedasys.com/davidw/

Gustav Paul

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May 29, 2007, 9:38:54 AM5/29/07
to rubyonra...@googlegroups.com
Hey

I had the same issue and settled for two cashed versions of my page, one
for logged in users and one for visitors.
I put the code changes into a plugin you might want to have a look at.

http://rails.co.za/articles/2007/01/10/cachefilter-update
and then some bug fixes later...
http://rails.co.za/articles/2007/02/07/cachefilter-rails-1-2-and-edge-compatible

HTH

Gustav Paul

davidn...@gmail.com

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May 29, 2007, 10:02:43 AM5/29/07
to Ruby on Rails: Talk
> > I have exactly the same need - a front page that has a bit of text
> > that changes depending on whether the user is logged in or not.
> > Everything else could be cached using page cacheing.

> I had the same issue and settled for two cashed versions of my page, one


> for logged in users and one for visitors.
> I put the code changes into a plugin you might want to have a look at.
>
> http://rails.co.za/articles/2007/01/10/cachefilter-update

> and then some bug fixes later...http://rails.co.za/articles/2007/02/07/cachefilter-rails-1-2-and-edge...

Looks like a good way of doing it.

I was thinking about something like this:

1) Create a no_cache method as a helper. The trick is that it outputs
something like <%= blah blah %>
2) Cache the page.
3) Render the cached version, which does the substitution on what
no_cache slipped into the cache.

I don't know whether how efficient that is, since the whole page still
has to be parsed up for erb, when there is only one little chunk of
it. I also don't know if there are any lurking problems...

davidn...@gmail.com

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May 29, 2007, 1:13:14 PM5/29/07
to Ruby on Rails: Talk
> I was thinking about something like this:
>
> 1) Create a no_cache method as a helper. The trick is that it outputs
> something like <%= blah blah %>
> 2) Cache the page.
> 3) Render the cached version, which does the substitution on what
> no_cache slipped into the cache.

Ok, some code that seems to work:

class NoCacheFilter

include ActionController::Caching::Actions

def initialize(*actions, &block)
@actions = actions
end

def before(controller)
return unless @actions.include?(controller.action_name.intern)
controller.instance_variable_set '@dont_interpolate_this', true
action_cache_path = ActionCachePath.new(controller)
if cache = controller.read_fragment(action_cache_path.path)
controller.rendered_action_cache = true
set_content_type!(action_cache_path)
controller.send(:render, :inline => cache)
false
end

end

def after(controller)
return if !@actions.include?(controller.action_name.intern) ||
controller.rendered_action_cache
controller.write_fragment(ActionCachePath.path_for(controller),
controller.response.body)
controller.send(:render, :inline => controller.response.body)
end

private
def set_content_type!(action_cache_path)
if extention = action_cache_path.extension
content_type = Mime::EXTENSION_LOOKUP[extention]
action_cache_path.controller.response.content_type =
content_type.to_s
end
end

end

Combined with this helper:

def no_cache(text)
return eval(text) unless @dont_interpolate_this
return "<%= #{text} %>"
end

Things that could perhaps be improved:

1) I don't like setting the variable in the controller.
2) I don't really like the fact that no_cache takes text as an
argument rather than somehow accomplishing the same thing with a
block, but there's no way to get a block's text out, so a string it
is, as far as I can tell.

davidn...@gmail.com

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May 29, 2007, 2:04:48 PM5/29/07
to Ruby on Rails: Talk
> def after(controller)
> return if !...@actions.include?(controller.action_name.intern) ||

> controller.rendered_action_cache
> controller.write_fragment(ActionCachePath.path_for(controller),
> controller.response.body)
> controller.send(:render, :inline => controller.response.body)
> end

Ugh, that isn't quite right, either, because apparently you can't do
any sort of render operation in the after filter, not even
render_to_string. This is pretty hacky feeling, but if that's what it
takes...

def after(controller)
return if !@actions.include?(controller.action_name.intern) ||
controller.rendered_action_cache
controller.write_fragment(ActionCachePath.path_for(controller),
controller.response.body)

controller.instance_variable_set '@performed_render', false
controller.response.body =
controller.send(:render_to_string, :inline =>
controller.response.body)
end

Cleaner ideas welcome!

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