1 files changed, 47 insertions, 0 deletions
diff --git a/railties/guides/source/active_support_overview.textile b/railties/guides/source/active_support_overview.textile
index d45aff81a0..aeaebe140e 100644
--- a/railties/guides/source/active_support_overview.textile
+++ b/railties/guides/source/active_support_overview.textile
@@ -138,6 +138,53 @@ user_path(@user) # => "/users/357-john-smith"
 
 WARNING. Controllers need to be aware of any redifinition of +to_param+ because when a request like that comes in "357-john-smith" is the value of +params[:id]+.
 
+h4. +to_query+
+
+Except for hashes, given an unescaped +key+ this method constructs the part of a query string that would map such key to what +to_param+ returns. For example, given
+
+<ruby>
+class User
+  def to_param
+    "#{id}-#{name.parameterize}"
+  end
+end
+</ruby>
+
+we get:
+
+<ruby>
+current_user.to_query('user') # => user=357-john-smith
+</ruby>
+
+This method escapes whatever is needed, both for the key and the value:
+
+<ruby>
+u.to_query('company[name]')
+# => "company%5Bname%5D=Johnson+%26+Johnson"
+</ruby>
+
+so its output is ready to be used in a query string.
+
+Arrays return the result of applying +to_query+ to each element with <tt>_key_[]</tt> as key, and join the result with "/":
+
+<ruby>
+[3.4, -45.6].to_query('sample')
+# => "sample%5B%5D=3.4&sample%5B%5D=-45.6"
+</ruby>
+
+Hashes also respond to +to_query+ but with a different signature. If no argument is passed a call generates a sorted series of key/value assigments calling +to_query(key)+ on its values. Then it joins the result with "&":
+
+<ruby>
+{:c => 3, :b => 2, :a => 1}.to_query # => "a=1&b=2&c=3"
+</ruby>
+
+The method +Hash#to_query+ accepts an optional namespace for the keys:
+
+<ruby>
+{:id => 89, :name => "John Smith"}.to_query('user')
+# => "user%5Bid%5D=89&user%5Bname%5D=John+Smith"
+</ruby>
+
 h3. Extensions to +Module+
 
 ...