Clarification of how controllers and views work together...

[Bob Hutchison]

On 17-Mar-07, at 2:10 PM, Ezra Zygmuntowicz wrote:

>
> On Mar 17, 2007, at 7:42 AM, Bob Hutchison wrote:
>
>> Hi Ezra,
>>
>> On 12-Mar-07, at 3:01 AM, Ezra Zygmuntowicz wrote:
>>
>>> 	Ok I took a look. Here is a patch for you to try before I commit  
>>> it to the repo. The default behavior remains the same and the  
>>> viewcontext is cached for subsequest renders. But if you pass  
>>> in  :clean_context => true  along with your render method you  
>>> will get a fresh context with your current ivars as you expect.
>>>
>>
>> That worked perfectly. Thanks!
>>
>> Just wondering... what do you gain by caching the ViewContext?  
>> Well, more precisely, when would the output of the render be  
>> different when using the cached ViewContext? Doesn't the  
>> ViewContext pretty much control the input to the rendering?  ... I  
>> suppose some of the view's input could be computed by calls (that  
>> changed the state of something, otherwise the result of the call  
>> would always be the same) made by the view but is that a good idea?
>>
>> Cheers,
>> Bob
>
>
> Hey Bob-
>
> 	If we don't cache the view context then layouts will not work  
> properly. The views that have layouts are rendered in a 2 step  
> process. First the inner template is rendered and an instance var  
> is set on the cached view context so when the layout gets rendered  
> that ivar is expanded to the layout content. If the view context is  
> not cached the layout will be empty, and its a performance hit to  
> copy ivars over twice.

Coincidentally I'm not using layouts, so I didn't seen any problems :-)

And you can't accomplish the same by caching the result in the case  
of layouts? Not via the view context, but an option maybe?

>
> 	You will notice rails does something similar by only allowing you  
> to render once. I don't limit you to rendering once and merb  
> renders just return strings and merb actions send whatever their  
> return value is to the browser.

I certainly did notice and I think what you've done is a very good  
idea. Very handy. I'm doing stuff in Merb that I can't do in Rails so  
I'm happy. I think this is a pretty nice feature that you should draw  
a bit of attention to.

Cheers,
Bob

>
> Cheers-
> -- Ezra Zygmuntowicz-- Lead Rails Evangelist
> -- ez at engineyard.com
> -- Engine Yard, Serious Rails Hosting
> -- (866) 518-YARD (9273)
>
>

----
Bob Hutchison                  -- tumblelog at <http:// 
www.recursive.ca/so/>
Recursive Design Inc.          -- <http://www.recursive.ca/>
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