ios cordite 读取错误CoreData could not fulfill a fault for '0x15b4a870

 

 

解释在这里

http://stackoverflow.com/questions/14296892/nsobjectinaccessibleexception-reason-coredata-could-not-fulfill-a-fault

这里是中文的详细解释

http://blog.csdn.net/meegomeego/article/details/17654947

 

需要参考的官方文档：

https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/CoreData/Articles/cdFaultingUniquing.html#//apple_ref/doc/uid/TP30001202-CJBDBHCB

 

从上面的文章中，你应该已经明白了fault的含义。这个单词的直接翻译是缺点，不足。在这里，就代表着一种不完全，部分获得的含义。

 

看了这个问题，我们再看看我今天用到的2个函数，用第一个函数时，程序就报错了，之后，改用第二个，解决了问题。

/* returns the object for the specified ID if it is already registered, otherwise it creates a fault corresponding to that objectID.  It never returns nil, and never performs I/O.  The object specified by objectID is assumed to exist, and if that assumption is wrong the fault may throw an exception when used. */

- (NSManagedObject *)objectWithID:(NSManagedObjectID *)objectID;    

 
/* returns the object for the specified ID if it is already registered in the context, or faults the object into the context.  It might perform I/O if the data is uncached.  If the object cannot be fetched, or does not exist, or cannot be faulted, it returns nil.  Unlike -objectWithID: it never returns a fault.  */

- (NSManagedObject*)existingObjectWithID:(NSManagedObjectID*)objectID error:(NSError**)error NS_AVAILABLE(10_6, 3_0);

 

 我们在来看看上面这2个函数的不同之处。

先看一下什么叫做registered：

All objects fetched from an external store are registered in a context together with a global identifier (an instance of NSManagedObjectID) that’s used to uniquely identify each object to the external store.