iOS RAC报错Cannot create __weak reference in file using manual reference counting

旧项目增添RAC时无法在手动计数文件中创建弱引用，出现以下报错 Cannot create __weak reference in file using manual reference counting

解决方式：

Build Settings ->

Apple Clang - Language - Objective C->

Weak Referances in Manual Retain Release ->

将NO改为YES