From 8458abb5e52dc38daa8176ed39d9dc45aa98f261 Mon Sep 17 00:00:00 2001
From: Xavier Noria <fxn@hashref.com>
Date: Sun, 23 Aug 2009 14:09:16 +0200
Subject: AS guide: documents key-based interpolation

---
 railties/guides/source/active_support_overview.textile | 13 +++++++++++++
 1 file changed, 13 insertions(+)

(limited to 'railties/guides/source')

diff --git a/railties/guides/source/active_support_overview.textile b/railties/guides/source/active_support_overview.textile
index 5e6c2030c6..06d750afc9 100644
--- a/railties/guides/source/active_support_overview.textile
+++ b/railties/guides/source/active_support_overview.textile
@@ -692,6 +692,19 @@ The method +String#squish+ strips leading and trailing whitespace, and substitut
 
 There's also the destructive version +String#squish!+.
 
+h4. Key-based Interpolation
+
+In Ruby 1.9 the <tt>%</tt> string operator supports key-based interpolation, both formatted and unformatted:
+
+<ruby>
+"Total is %<total>.02f" % {:total => 43.1}  # => Total is 43.10
+"I say %{foo}" % {:foo => "wadus"}          # => "I say wadus"
+"I say %{woo}" % {:foo => "wadus"}          # => KeyError
+</ruby>
+
+Active Support adds that functionality to <tt>%</tt> in previous versions of Ruby.
+
+
 h3. Extensions to +Numeric+
 
 ...
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