From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2012-06-20T22:51:27+09:00
Subject: Re: Does ERB have recursive template support?

On Wed, Jun 20, 2012 at 3:24 PM, Robert Klemme
<shortcutter@googlemail.com> wrote:
> On Wed, Jun 20, 2012 at 1:53 PM, Jesús Gabriel y Galán
> <jgabrielygalan@gmail.com> wrote:
>
>> 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."
>
> You are doing too much file reading here because you reread the
> template file for each value.  That's not necessary since we can use
> parameter binding.

You are right. I was focusing on the temporary erbout variable approach.

>
>> 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 think the trick lies in getting bindings properly by nesting them
> properly.  My first naive approaches did not work because variables
> were overwritten.
>
>> I don't know how you represent your nested objects. In this example I
>> created an array through which I recursively generate a template.
>
> Same here:
>
> #!/opt/bin/ruby19
>
> require 'erb'
>
> def rt(s)
>  e = ERB.new(s)
>  recursive = lambda {|a, level| e.result(binding)}
> end
>
> arr = [
>  1,
>  2,
>  [3],
>  [4, [5]],
>  6
> ]
>
> e = rt %Q{
>  <%= '  ' * level %>open level=<%= level %>
>  <%
>    if Enumerable === a
>      a.each do |x|
>        %><%= recursive[x, level + 1] %><%
>      end
>    else
>      %><%= '  ' * level %><%= a %><%
>    end
>  %>
>  <%= '  ' * level %>close level=<%= level %>
> }
>
> p arr
> puts e[arr, 0]

Very nice and elegant. Thanks !

Jesus.