objective c - How to list out Recently Opened documents in iOS? -

i have listed out documents in nsdocument directory , im able documents modified using :

nsmutablearray* filesandproperties = [nsmutablearray arraywithcapacity:[filesarray count]]; for(nsstring* file in filesarray) {     nsstring* filepath = [imgr.documentspath stringbyappendingpathcomponent:file];     nsdictionary* properties = [[nsfilemanager defaultmanager]                                 attributesofitematpath:filepath                                 error:&error];     nsdate* moddate = [properties objectforkey:nsfilemodificationdate];      if(error == nil)     {         [filesandproperties addobject:[nsdictionary dictionarywithobjectsandkeys:                                        file, @"path",                                        moddate, @"lastmoddate",                                        nil]];                      } } 

by fallowing : get directory contents in date modified order

now how can list out documents have been opened , viewed user without editing or modifications ?