Merge pull request #129 from YasuOza/direct_attributes_from_array

Direct attributes from array

README.md

@@ -77,6 +77,16 @@ end
 # => [ { "name": "David", "age": 32 }, { "name": "Jamie", "age": 31 } ]
 ```
 
+You can also extract attributes from array directly.
+
+``` ruby
+# @people = People.all
+json.array! @people :id :name
+
+# => [ { "id": 1, "name": "David" }, { "id": 2, "name": "Jamie" } ]
+```
+
+
 Jbuilder objects can be directly nested inside each other.  Useful for composing objects.
 
 ``` ruby

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

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 = []