softcraft-development · June 13, 2010 19:19 · Jun 13, 2010
diff --git a/add_collection_associations_to_factory_girl_factories.rb b/add_collection_associations_to_factory_girl_factories.rb
@@ -0,0 +1,30 @@
+# Goal: Allow addition of instances to a collection in a factory-built object
+# when those instances require references to the parent.
+# Typically occurs in Rails when one model has_many instances of another
+
+# See more at:
+# http://stackoverflow.com/questions/2937326/populating-an-association-with-children-in-factory-girl
+
+class Factory
+  def has_many(collection)
+    # after_build is where you add instances to the factory-built collection. 
+    # Typically you'll want to Factory.build() these instances.
+    after_build { |instance|
+      yield instance
+    }
+
+    # after_create will be called after after_build if the build strategy is Factory.create()
+    after_create { |instance|
+      instance.send(collection).each { |i| i.save! }
+    }
+  end
+end
+
+# Usage
+# Foo has_many :bar
+
+Factory.define :foo do |f|
+  f.has_many :bar do |foo|
+    foo.bar << Factory.build(:bar, :foo => foo)
+  end
+end
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