[Zope3-dev] Re: Re: tal:define="..." considered harmful?

Martijn Faassen faassen at infrae.com
Thu Feb 16 12:54:55 EST 2006

Jean-Marc Orliaguet wrote:
> Martijn Faassen wrote:
>> It had unit tests, and the regex stuff that I was referring to may be
>> interesting - it ports the regexes from Zope's TALES to Javascript so
>> that the parsing of tales expressions works the same.
>> This is the module that has the regex bits, ported directly, if I 
>> recall correctly, from Zope's python code:
>> https://infrae.com/svn/sapling/trunk/zpt/talparser.js
> OK I see, it's the variable substitution;
> string:${name}/${address} ..

I don't think it has an implementation of string TALES expressions.

It's parsing anything that's actually *inside* the attributes you add on 
HTML with tal, such as detecting whether a TALES expression type 
identifier is used ('string:' or 'python:', say), or 'structure', and 
the right splitting of tal:repeat="foo bar" (into 'foo' and 'bar'), and 
semicolons for multiple attributes with tal:attributes, and so on. I 
just literally ported that code to javascript from Zope's implementation 
  so it follows the established rules pretty well.

>> More in general, it's possible that some template will receive two 
>> sets of data that's quite separate from each other. I like namespaces 
>> then too. You can of course always argue that such a template should 
>> be factored into multiple smaller ones, though the question remains 
>> how they'd each receive only their data and not the rest.

> what I mean it that the structures can always be merged before they are 
> passed to the template, then the data can be organized as:
> data = {
>  items: [ ...],
>  people: [],
>  somemoredata: {}
> }
> ZPT does a mapping between several data structures (context, request, 
> view ...) and the variables with the same name in TAL, which results in 
> several namespaces. Such variables are very platform-dependent and a 
> templating language basically needs only one data structure to do the 
> rendering..

I'm not sure I understand fully... Perhaps you mean this:

A pattern in templating is to prepare the data fully in nested 
dictionaries and lists with simple strings and integers inside before 
the data is pushed along to a template, as opposed to the template 
pulling it out of request and context and view individually (with method 
calls, often). Perhaps you are referring to this pattern. I like this 
pattern, as it has positive qualities concerning debuggability, 
modularity, loose coupling and makes possible various performance 

XSLT and ClearSilver are templating languages which have this pattern. 
TAL can be made to follow this pattern with some small modifications.



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