OpenStruct#dig

* lib/ostruct.rb (dig): Implement OpenStruct#dig
  [Feature #11688]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52611 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,8 @@
+Tue Nov 17 14:36:00 2015  Kenichi Kamiya  <kachick1@gmail.com>
+
+	* lib/ostruct.rb (dig): Implement OpenStruct#dig
+	  [Feature #11688]
+
 Tue Nov 17 14:04:14 2015  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* ext/socket/lib/socket.rb (Socket#recvmsg{,_nonblock}): default values

lib/ostruct.rb

@@ -214,6 +214,24 @@ class OpenStruct
     modifiable[new_ostruct_member(name)] = value
   end
 
+  #
+  # Retrieves the value object corresponding to the each +name+
+  # objects repeatedly.
+  #
+  #   address = OpenStruct.new('city' => "Anytown NC", 'zip' => 12345)
+  #   person = OpenStruct.new('name' => 'John Smith', 'address' => address)
+  #   person.dig(:address, 'zip') # => 12345
+  #   person.dig(:business_address, 'zip') # => nil
+  #
+  def dig(name, *names)
+    begin
+      name = name.to_sym
+    rescue NoMethodError
+      return
+    end
+    @table.dig(name, *names)
+  end
+
   #
   # Remove the named field from the object. Returns the value that the field
   # contained if it was defined.

test/ostruct/test_ostruct.rb

@@ -108,6 +108,17 @@ class TC_OpenStruct < Test::Unit::TestCase
     assert_equal :bar, os['foo']
   end
 
+  def test_dig
+    os1 = OpenStruct.new
+    os2 = OpenStruct.new
+    os1.child = os2
+    os2.foo = :bar
+    os2.child = [42]
+    assert_equal :bar, os1.dig("child", :foo)
+    assert_nil os1.dig("parent", :foo)
+    assert_nil os1.dig("child", 0)
+  end
+
   def test_to_h
     h = {name: "John Smith", age: 70, pension: 300}
     os = OpenStruct.new(h)