ignore! function added

lib/jbuilder.rb

@@ -14,6 +14,7 @@ def initialize(options = {})
 
     @key_formatter = options.fetch(:key_formatter){ @@key_formatter ? @@key_formatter.clone : nil}
     @ignore_nil = options.fetch(:ignore_nil, @@ignore_nil)
+    @ignore_block = nil
 
     yield self if ::Kernel.block_given?
   end
@@ -106,6 +107,24 @@ def self.key_format(*args)
     @@key_formatter = KeyFormatter.new(*args)
   end
 
+  # If you want to skip adding some values to your JSON hash like empty string
+  # or empty array, you can pass a block.
+  #
+  # Example:
+  #   json.ignore! { |value| value.nil? }
+  #   json.id       User.new.id
+  #   json.email    ''
+  #   {"emails" : '' }
+  #
+  #   json.ignore! { |value| value.nil? || (value.respond_to?(:empty) && value.empty?) }
+  #   json.id       User.new.id
+  #   json.email   ''
+  #   { }
+  #
+  def ignore!(&block)
+    @ignore_block = block
+  end
+
   # If you want to skip adding nil values to your JSON hash. This is useful
   # for JSON clients that don't deal well with nil values, and would prefer
   # not to receive keys which have null values.
@@ -288,11 +307,15 @@ def _key(key)
   def _set_value(key, value)
     raise NullError.build(key) if @attributes.nil?
     raise ArrayError.build(key) if ::Array === @attributes
-    return if @ignore_nil && value.nil? or _blank?(value)
+    return if _ignore_value?(value) or _blank?(value)
     @attributes = {} if _blank?
     @attributes[_key(key)] = value
   end
 
+  def _ignore_value?(value)
+    (@ignore_nil && value.nil?) || (@ignore_block && @ignore_block.call(value))
+  end
+
   def _map_collection(collection)
     collection.map do |element|
       _scope{ yield element }

test/jbuilder_test.rb

@@ -603,6 +603,17 @@ class JbuilderTest < ActiveSupport::TestCase
     assert_equal ['name', 'dne'], result.keys
   end
 
+  test 'ignore! with block' do
+    result = jbuild do |json|
+      json.ignore! { |value| value.blank? }
+      json.name 'Bob'
+      json.list []
+      json.email ''
+      json.dne nil
+    end
+    assert_equal ['name'], result.keys
+  end
+
   test 'default ignore_nil!' do
     Jbuilder.ignore_nil