From: Robert Klemme <shortcutter@...>
Date: 2012-06-20T22:24:30+09:00
Subject: Re: Does ERB have recursive template support?

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.

> 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]

Kind regards

robert



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