Merge pull request rails#23 from bigjason/nestable-jbuilder

Allow nesting of Jbuilder objects

README.md

@@ -66,6 +66,34 @@ end
 # => [ { "name": David", "age": 32 }, { "name": Jamie", "age": 31 } ]
 ```
 
+Jbuilder objects can be directly nested inside each other.  Useful for composing objects.
+
+``` ruby
+class Person
+  # ... Class Definition ... #
+  def to_builder
+    person = Jbuilder.new
+    person.(self, :name, :age)
+    person
+  end
+end
+
+class Company
+  # ... Class Definition ... #
+  def to_builder
+    company = Jbuilder.new
+    company.name name
+    company.president president.to_builder
+    company
+  end
+end
+
+company = Company.new("Doodle Corp", Person.new("John Stobs", 58))
+company.to_builder.target!
+
+# => {"name":"Doodle Corp","president":{"name":"John Stobs","age":58}}
+```
+
 You can either use Jbuilder stand-alone or directly as an ActionView template language. When required in Rails, you can create views ala show.json.jbuilder (the json is already yielded):
 
 ``` ruby

lib/jbuilder.rb

@@ -14,6 +14,8 @@ def self.encode
 
   define_method(:__class__, find_hidden_method(:class))
   define_method(:_tap, find_hidden_method(:tap))
+  define_method(:_is_a?, find_hidden_method(:is_a?))
+  reveal(:respond_to?)
 
   def initialize(key_format = @@key_format.clone)
     @attributes = ActiveSupport::OrderedHash.new
@@ -178,6 +180,12 @@ def target!
   private
     def method_missing(method, *args)
       case
+      # json.age 32
+      # json.person another_jbuilder
+      # { "age": 32, "person": { ...  }
+      when args.one? && args.first.respond_to?(:_is_a?) && args.first._is_a?(Jbuilder)
+        set! method, args.first.attributes!
+
       # json.comments @post.comments { |json, comment| ... }
       # { "comments": [ { ... }, { ... } ] }
       when args.one? && block_given?
@@ -192,7 +200,7 @@ def method_missing(method, *args)
       # { "comments": ... }
       when args.empty? && block_given?
         _yield_nesting(method) { |jbuilder| yield jbuilder }
-      
+
       # json.comments(@post.comments, :content, :created_at)
       # { "comments": [ { "content": "hello", "created_at": "..." }, { "content": "world", "created_at": "..." } ] }
       when args.many? && args.first.is_a?(Enumerable)

test/jbuilder_test.rb

@@ -208,7 +208,19 @@ def initialize(name, age)
 
     assert_equal "david", JSON.parse(json)["comments"].first["authors"].first["name"]
   end
-
+
+  test "nested jbuilder objects" do
+    to_nest = Jbuilder.new
+    to_nest.nested_value "Nested Test"
+    json = Jbuilder.encode do |json|
+      json.value "Test"
+      json.nested to_nest
+    end
+    parsed = JSON.parse(json)
+    assert_equal "Test", parsed['value']
+    assert_equal "Nested Test", parsed["nested"]["nested_value"]
+  end
+
   test "top-level array" do
     comments = [ Struct.new(:content, :id).new("hello", 1), Struct.new(:content, :id).new("world", 2) ]