[ZPT] Page Template Preconditions?

[Jim Fulton]

Evan Simpson wrote:
> Jeffrey P Shell wrote:
> 
>> So then I tried doing a <..tal:define="dummy
>> python:here.checkSession(...)">, but in any combination I tried the 
>> redirect
>> never happened - raising one just brought up TALESError, and I think a
>> 'RESPONSE.redirect(...)' call just got swallowed.
> 
> 
> These should both work :-(

I wonder why they didn't. This doesn't seem like it should be
hard to do.


>> So what I'm wondering is if there's been any thoughts to doing some 
>> sort of
>> 'precondition' script/expression, or adding in some event hooks to Page
>> Templates?  ASP.NET (and possibly earlier versions) has a Page_Load(...)
>> event handler that developers can write.
> 
> 
> I have developed a pattern for pages that require a lot of prep work 
> (especially form/wizard participants) that involves directing all 
> requests to a Script.  The Script does the prep, then usually ends with 
> a 'return container['scriptname.pt'](somedata=somedata)'.


I have a similar pattern, except, I usually have a single define
at the top of the template that calls a Python method that computes
a data structure containing the things I need.

> It would certainly be possible to add a 'pre-publish' field to ZPT, with 
> the value interpreted as a TALES expression.  I would expect this to be 
> evaluated only when the ZPT is being published directly, not when it's 
> called from other code.  The only questions remaining in my mind would 
> be how to best make the ZPT object available to the Script (if the 
> expression calls a Script) and how to interpret the value of the 
> expression.  If the expression evaluates to a tuple, list, or mapping, 
> it would be straightforward to place in 'options'.  It might be helpful 
> to interpret a string as "publish this instead of the template".  What 
> about other values?

This all sounds too complicated to me. Surely, we don't need this.

Jim

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