將NSCalendarDate轉換爲xml文件並返回__NSTaggedDate

Question

在Objective-C（OS X 10.9）中，我編寫了一個NSDictionary以便與[MyDict writeToFile:SavePath atomically:YES];一起存檔。我恢復字典與MyDict = [NSDictionary dictionaryWithContentsOfFile:filePath];

但是，然後我遇到一個包含NSCalendarDate對象的鍵不再是NSCalendarDate，而是__NSTaggedDate。這使我有以下錯誤：

2016-09-06 09:19:39.957 MyProject[720:303] -[__NSTaggedDate yearOfCommonEra]: unrecognized selector sent to instance 0x41bd7801f000000d 

上的代碼行：

if([AtTansaction.TransactionDate yearOfCommonEra] == DataArray[cnt].year) 

因此，如何重建一個NSCalendarDate？什麼是NSTaggedDate？

Answer 1

好的，我發現了錯誤。 NSDictionary只保存NSDate s，而不是NSCalendarDate s。返回的對象是__NSTaggedDate，它繼承自NSDate。我發現這個通過調用：DumpObjcMethods(object_getClass(_StartDate))在對象上和它的超類：

Found 9 methods on '__NSTaggedDate' 
'__NSTaggedDate' has method named 'dealloc' of encoding 'v16@0:8' 
'__NSTaggedDate' has method named 'timeIntervalSinceReferenceDate' of encoding 'd16@0:8' 
'__NSTaggedDate' has method named 'initWithTimeIntervalSinceReferenceDate:' of encoding '@24@0:8d16' 
'__NSTaggedDate' has method named 'isInToday' of encoding 'c16@0:8' 
'__NSTaggedDate' has method named 'isInTomorrow' of encoding 'c16@0:8' 
'__NSTaggedDate' has method named 'isInYesterday' of encoding 'c16@0:8' 
'__NSTaggedDate' has method named 'isInSameDayAsDate:' of encoding 'c24@0:8@16' 
'__NSTaggedDate' has method named 'isEqual:toUnitGranularity:' of encoding 'c32@0:8@16Q24' 
'__NSTaggedDate' has method named 'compare:toUnitGranularity:' of encoding 'q32@0:8@16Q24' 

幸運的是，我可以NSDate S（並且因此__NSTaggedDate）轉換爲與NSCalendarDate _StartDate = [NSCalendarDate dateWithTimeInterval：0 sinceDate：_StartDate];