From c2b966cf653ea4264fbb008b8cc6ce5359ebe40a Mon Sep 17 00:00:00 2001
From: Yasuharu Ozaki <yasuharu.ozaki@gmail.com>
Date: Wed, 24 Apr 2013 16:59:02 +0900
Subject: [PATCH] Allow quick extract attributes from array

---
 lib/jbuilder.rb       |  6 ++++--
 test/jbuilder_test.rb | 14 ++++++++++++++
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/lib/jbuilder.rb b/lib/jbuilder.rb
index f96bc99..ffece0e 100644
--- a/lib/jbuilder.rb
+++ b/lib/jbuilder.rb
@@ -224,8 +224,10 @@ def child!
   #   json.array! [1, 2, 3]
   #
   #   [1,2,3]
-  def array!(collection, &block)
-    @attributes = if ::Kernel::block_given?
+  def array!(collection, *attributes, &block)
+    @attributes = if attributes.present?
+      _map_collection(collection) { |element| extract!(element, *attributes) }
+    elsif ::Kernel::block_given?
       _map_collection(collection) { |element| block.arity == 2 ? block[self, element] : block[element] }
     else
       collection
diff --git a/test/jbuilder_test.rb b/test/jbuilder_test.rb
index 9923d81..1754d9f 100644
--- a/test/jbuilder_test.rb
+++ b/test/jbuilder_test.rb
@@ -367,6 +367,20 @@ def initialize(name, age)
     assert_equal 'world', parsed.second['content']
   end
 
+  test 'extract attributes directly from array' do
+    comments = [ Comment.new('hello', 1), Comment.new('world', 2) ]
+
+    json = Jbuilder.encode do |json|
+      json.array! comments, :content, :id
+    end
+
+    parsed = MultiJson.load(json)
+    assert_equal 'hello', parsed.first['content']
+    assert_equal       1, parsed.first['id']
+    assert_equal 'world', parsed.second['content']
+    assert_equal       2, parsed.second['id']
+  end
+
   test 'empty top-level array' do
     comments = []