From: Gavin Kistner <gavin@...>
Date: 2005-08-19T23:33:53+09:00
Subject: Re: #puts inside ERB

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On Aug 19, 2005, at 2:07 AM, Mark Hubbart wrote:
> How about this? Still somewhat hacky, but maybe less breakable. It
> should work unless you supply a binding in the Kernel module context;
> the new #puts is defined in Object.

Tricky! I moved the module into ERB::Writeable.

Despite your super calls, I used Object.class_eval to dynamically  
override #puts, #print and #p at the start of ERB#result, and then  
undefs those methods at the end of #result. It's sure to be more of a  
performance hit (though I'll have to benchmark to see how much it  
affects things) but I wanted to really leave the house as clean when  
I left as when I entered.

Oh, I also needed to add some .to_s calls inside Writeable's methods,  
to handle non-string arguments.

In summary (for the google-able archives): using Mark's technique, I  
have made a patched version of ERB which causes calls to puts, print,  
and p inside an ERB to place their information into the ERB output  
string, instead of immediately sending the results to $stdout. (If  
you use this patch but need some debug information in your ERB  
template, you can still use $stdout.puts to hide output from the ERB  
string.)

You can download the patched file from http://phrogz.net/RubyLibs/ 
erb_1.8.2_with_puts.rb.gz
After ungzipping, the file should be renamed to 'erb.rb' and replace  
the file in (for a standard install):
/usr/local/lib/ruby/1.8/erb.rb


Finally, for the naysayers (and the archive), this functionality  
(using Ruby code inside an ERB template to inject strings into the  
ERB template in place without using <%=...%>) can be achieved without  
the above patch by using the "eoutvar" option for ERB. By default,  
this is a local variable named "_erbout", but you can name it  
whatever you wish by modifying the fourth parameter to ERB.new. For  
example:

require 'erb'

template1 = <<'ENDTEMPLATE'
Hello
<% 1.upto(9){ |i|
     _erbout << "\t#{i} x #{i} = #{i*i}"
     _erbout << "\n" unless i==9
} %>
Goodbye
ENDTEMPLATE
ERB.new( template1 ).run

template2 = <<'ENDTEMPLATE'
Hello
<% 1.upto(9){ |i|
     OUTPUT << "\t#{i} x #{i} = #{i*i}"
     OUTPUT << "\n" unless i==9
} %>
Goodbye
ENDTEMPLATE
ERB.new( template2, nil, nil, 'OUTPUT' ).run


Both of the above output:
Hello
     1 x 1 = 1
     2 x 2 = 4
     3 x 3 = 9
     4 x 4 = 16
     5 x 5 = 25
     6 x 6 = 36
     7 x 7 = 49
     8 x 8 = 64
     9 x 9 = 81
Goodbye
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