[antlr-interest] StringTemplate "reflection" enhancement

[Terence Parr]

Ok, I just found an objection.  $x.y$ currently looks up y in the 
attribute table of x if x is a ST.  This is consistent with the use of 
$super.attribute$ and $super.templateRef()$.  Hmm...so $self.name$ 
doesn't work: it looks for attribute name in the attribute list not 
getName() in ST self.  Argh!!!!

Any suggestions?  I don't want to make self special obviously and 
behave differently than any other reference to a template variable.

Perhaps we throw out self and use just a plain attribute reference that 
is special like $attributes$, which you could then walk with ST.  The 
negative is that it would unnecessarily expensive to compute 
"attributes" and have it laying around all the time.   Perhaps it's 
only available in "lint mode", which already exists?

$attributes:{Name: $it.name$ Type: $it.type.name$ 
Properties:$it.properties$}$

Also, what if a an attribute is multi-valued?  Before I had this:

> Name: user
> Type: org.foo.MyUser
> Properties: name, email, address, phone

but what if it's really say 2 users:

Name: users
Type: org.foo.MyUser
Properties: name, email, address, phone
Type: org.foo.MyUser
Properties: name, email, address, phone

oh, i guess ST would handle that automatically with template 
application.

Now, what about properties that have properties.  For example,

Name: student
Type: org.foo.Student
Properties: name, school, ID

where school property is actually an aggregate with properties too or 
worse a ST itself?  You must recurse.  Since this could go 10 levels 
deep, I'm not sure if it's worth digging down into subproperties of 
subproperties etc...

Ter

On Sep 25, 2004, at 1:31 PM, Terence Parr wrote:

> Howdy,
>
> When debugging templates particularly for web pages with lots of nested
> templates, printing out the list of attributes you've set with
> setAttribute() is pretty handy.  You could, for example, display the
> contents of all attributes at the bottom of a web page if in "debug"
> mode.  So if you had set two attributes title (a simple string) and
> user (a user-defined object), you might want this info:
>
> Name: title
> Type: java.lang.String
>
> Name: user
> Type: org.foo.MyUser
> Properties: name, email, address, phone
>
> It shows the incoming data not the references in the template.
>
> Seems like this can be easily had by allowing templates to access the
> list of attribute name/value pairs via a reflection method.  We'd want
> this to be on-demand rather than computing a set of reflection
> descriptors each time.  Rather than make a special attribute, we should
> make it something like <self.attributes> which will on demand (when
> rendered) call getAttributes() on "self" (the template object).
>
> <self.attributes> would return not the raw attribute data, but a
> reflection object that describes the key/value pair.  That reflection
> object would let you say:
>
> <self.attributes:{Name: <it.name> Type: <it.type.name> Properties:
> <it.properties>}>
>
> Further you want to be able to be able to recursively walk down to
> embedded templates and get those attributes.  You'd probably want a
> flattened list of all attributes for any particular page.  Perhaps that
> requires <self.embedded> or <self.children> so you can use
> StringTemplate to walk down to those templates. :)
>
> All I have to do is set "self" to be a predefined attribute pointing to
> the surrounding template "this" pointer and all this will just work.
> <self.name> etc... will just work as they are getXXX methods already
> defined.
>
> Hmm...anybody have any suggestions or problems with this approach?
>
> Thanks,
> Ter
> --
> CS Professor & Grad Director, University of San Francisco
> Creator, ANTLR Parser Generator, http://www.antlr.org
> Cofounder, http://www.jguru.com
> Cofounder, http://www.knowspam.net enjoy email again!
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--
CS Professor & Grad Director, University of San Francisco
Creator, ANTLR Parser Generator, http://www.antlr.org
Cofounder, http://www.jguru.com
Cofounder, http://www.knowspam.net enjoy email again!





 
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