class Api::V3::Detail::RunSerializer < Api::V3::ApplicationSerializer
  belongs_to :user, serializer: Api::V3::UserSerializer
  belongs_to :game, serializer: Api::V3::GameSerializer
  belongs_to :category, serializer: Api::V3::CategorySerializer
  has_one :time

  attributes :id, :path, :name, :program, :image_url, :created_at, :updated_at, :video_url, :splits

  def splits
    object.splits.map do |segment|
      segment.best = {duration: segment.best}
      segment
    end
  end
end

class Api::V3::Detail::RunSerializer < Api::V3::ApplicationSerializer
  belongs_to :user, serializer: Api::V3::UserSerializer
  belongs_to :game, serializer: Api::V3::GameSerializer
  belongs_to :category, serializer: Api::V3::CategorySerializer
  has_one :time

  attributes :id, :path, :name, :program, :image_url, :created_at, :updated_at, :video_url, :splits
end

--- 
+++ 
@@ -5,4 +5,11 @@
   has_one :time
 
   attributes :id, :path, :name, :program, :image_url, :created_at, :updated_at, :video_url, :splits
+
+  def splits
+    object.splits.map do |segment|
+      segment.best = {duration: segment.best}
+      segment
+    end
+  end
 end
Put api v3 best durations back in a best hash
