From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2012-06-20T20:53:38+09:00
Subject: Re: Does ERB have recursive template support?

On Wed, Jun 20, 2012 at 3:22 AM, Todd Wei <lists@ruby-forum.com> wrote:
> Robert Klemme wrote in post #1065085:
>>
>> What exactly do you mean by "recursive templates"?  Do you mean a
>> template which can present recursive structures such as trees?  Or do
>> you want an ERB template to include itself?  Both should be doable
>> since you can invoke arbitrary code.
>>
>> Kind regards
>>
>> robert
>
> My code generator will generate Java nested classes. The problem is the
> level of nesting can't be determined statically. So, the ideal case is I
> define a Java class template in ERB, which accepts binding variables as
> input
> parameter, and in the template, it can "call" itself with new bindings.
> Just like what does recursive function do.
>
> I'm not sure if i can achieve this with "invoke arbitrary code". For
> example, can I invoke the template itself with new bindings in the
> template? Could you give me an example? Thanks!

If I understood correctly, something like this could work for you:

# template.rb

this template contains:
<%= array.inspect %>
<%
first = array.shift
if first
%>
<%= first %>,
<%= ERB.new(File.read("template.erb"), 0, "",
"result_#{array.length}").result(binding) %>
<%
end
%>
and something else.

1.9.2p290 :041 > array = [1,2,3,4]; ERB.new(File.read("template.erb"),
0, "", "result_#{array.length}").result(binding)
 => "this template contains:\n[1, 2, 3, 4]\n\n1,\nthis template
contains:\n[2, 3, 4]\n\n2,\nthis template contains:\n[3,
4]\n\n3,\nthis template contains:\n[4]\n\n4,\nthis template
contains:\n[]\n\nand something else.\n\nand something else.\n\nand
something else.\n\nand something else.\n\nand something else."

The trick is to create a unique temporary variable for the ouput of
each iteration. If not, erb will overwrite the result of each
iteration.
I don't know how you represent your nested objects. In this example I
created an array through which I recursively generate a template.

I hope this gives you some ideas.

Jesus.