All array properties will return a default collection proxy if nil.

Changes.md

@@ -2,6 +2,7 @@
 
 ### 1.7.2
 - FIXED: first_or_create will now apply dirty tracking to newly created fields.
+- FIXED: Properties of :array type will always return a Parse::CollectionProxy if their internal value is nil. The object will not be marked dirty until something is added to the array.
 - NEW: `Parse::Model.autosave_on_create` has been removed in favor of `first_or_create!`.
 - FIXED: Encoding a Parse::Object into JSON will remove any values that are `nil`
 which were not explicitly changed to that value.

lib/parse/model/core/properties.rb

@@ -300,6 +300,12 @@ def property(key, data_type = :string, **opts)
             # lets set the variable with the updated value
              instance_variable_set ivar, value
              send will_change_method
+          elsif value.nil? && data_type == :array
+            value = Parse::CollectionProxy.new [], delegate: self, key: key
+            instance_variable_set ivar, value
+            # don't send the notification yet until they actually add something
+            # which will be handled by the collection proxy.
+            # send will_change_method
           end
 
           # if the value is a String (like an iso8601 date) and the data type of