Blocks in pure ERB / Erubis - ruby

Question

I have the following Ruby script:
require 'erubis'
def listing(title, attributes={})
"output" + yield + "more output"
end
example = %Q{<% listing "db/migrate/[date]_create_purchases.rb", :id => "ch01_292" do %>
<![CDATA[class CreatePurchases < ActiveRecord::Migration
def change
create_table :purchases do |t|
t.string :name
t.float :cost
t.timestamps
end
end
end]]>
<% end %>}
chapter = Erubis::Eruby.new(example)
p chapter.result(binding)
I am attempting to use a block here and get it to output "output", then the content in the block and then "more output", but I can't seem to get it to work.
I know that ERB used to work this way in Rails 2.3 and now works with <%= in Rails 3... but I'm not using Rails at all. This is just pure ERB.
How can I get it to output all the content?

Answer 1

Jeremy McAnally linked me to this perfect description of how to do it.
Basically, you need to tell ERB to store the output buffer in a variable.
The script ends up looking like this:
require 'erb'
def listing(title, attributes={})
concat %Q{
<example id='#{attributes[:id]}'>
<programlisting>
<title>#{title}</title>}
yield
concat %Q{
</programlisting>
</example>
}
end
def concat(string)
#output.concat(string)
end
example = %Q{<% listing "db/migrate/[date]_create_purchases.rb", :id => "ch01_292" do %>
<![CDATA[class CreatePurchases < ActiveRecord::Migration
def change
create_table :purchases do |t|
t.string :name
t.float :cost
t.timestamps
end
end
end]]>
<% end %>}
chapter = ERB.new(example, nil, nil, "#output")
p chapter.result(binding)

Answer 2

Great. I remember seeing that a while ago. Playing a bit I was getting this:
require 'erubis'
def listing(title, attributes={})
%Q{<%= "output #{yield} more output" %>}
end
example = listing "some title", :id => 50 do
def say_something
"success?"
end
say_something
end
c = Erubis::Eruby.new(example)
p c.evaluate
# => "output success? more output"