On Tue, Sep 22, 2009 at 3:29 PM, Steven Roussey <[email protected]> wrote:
>
>> > {.section post}
>> > Title: {title}
>> > Body: {body}
>> > {section @ @.parent.is-moderator?}
>>
>> Why do you need that? I think it's a lot simpler if you if you leave
>> out the "predicate_scope" and just have the predicate have access to
>> the whole stack of namespaces, as I described in the bug.
>
> But then everything has to be a predicate function. Which has to be
> implemented in both JS and the server side language. If you have
> someone (like a designer) working on templates, they are not the same
> person writing the JS/PHP/etc. And it's easier to have someone add an
> extra node to JSON than to write extra functions to check on that
> extra node in the json.
Right. So I think the answer is that predicates need to be able to
take arguments, just like formatters can. So the original syntax
{.section node predicate?}
isn't sufficient. As I mentioned formatters don't really take
arguments -- the thing after | in {foo|...} is an uninterpreted string
to JSON template, and the app code can interpret things as arugments.
So then everything after the node name and before | can also be an
uninterpreted string (althoug this conflicts a bit with
http://code.google.com/p/json-template/issues/detail?id=26)
The syntax I think is fairly similar to what you propose, but it's an
important difference.
{.section <node> <predicate>}
So you can spell it like:
{.section @ true? moderator}
<button {id}>
{.end}
IMO that is a little ugly, so I would prefer to come up with a convention like:
{.section @ if-moderator}
{.section @ if-base-url}
"if-" is a prefix, and then the thing after the - is a string which
you can test for. This is the most flexible thing, and adds less
complexity than argument parsing in the template language itself.
def Predicates(p):
if p.startswith("if-"):
return lambda context: bool(context.Lookup(p[len("if-") : ]) #
look up "moderator" in the context, and return its truth value
else:
return None
t = Template(predicates=Predicates)
Does that make sense? It's higher order functional programming again.
Andy
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