将NSCalendarDate转换为xml文件并返回__NSTaggedDate

Question

在Objective-C（OS X 10.9）中，我编写了一个NSDictionary以便与[MyDict writeToFile:SavePath atomically:YES];一起存档。我恢复字典与MyDict = [NSDictionary dictionaryWithContentsOfFile:filePath];

但是，然后我遇到一个包含NSCalendarDate对象的键不再是NSCalendarDate，而是__NSTaggedDate。这使我有以下错误：

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

上的代码行：

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

因此，如何重建一个NSCalendarDate？什么是NSTaggedDate？

Answer 1

好的，我发现了错误。 NSDictionary只保存NSDate s，而不是NSCalendarDate s。返回的对象是__NSTaggedDate，它继承自NSDate。我发现这个通过调用：DumpObjcMethods(object_getClass(_StartDate))在对象上和它的超类：

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' 

幸运的是，我可以NSDate S（并且因此__NSTaggedDate）转换为与NSCalendarDate _StartDate = [NSCalendarDate dateWithTimeInterval：0 sinceDate：_StartDate];