我正在尝试使用-[NSObjectautoContentAccessingProxy]如http://developer.apple.com/library/ios/documentation/Cocoa/Reference/Foundation/Classes/nsobject_Class/Reference/Reference.html#//apple_ref/occ/instm/NSObject/autoContentAccessingProxy所述.我尝试代理的对象实现了NSDiscardableContent协议(protocol)和-autoContentAccessing