如何获取Core Data数据库的最后一条记录？ [英] How do I get the last record of a Core Data database?

问题描述

我有一个名为images的核心数据实体，只有2个字段：

I have a core data entity called images that has just 2 fields:

imageName = NSString
timeStamp = NSNumber

我试图模拟一种堆栈LIFO（后进先出）。
插入新条目很容易，但是如何读取添加到实体的最后一个条目呢？

I am trying to simulate a kind of stack LIFO (last in first out). Inserting a new entry is easy but what about reading the last entry added to the entity?

所有图像都添加了时间戳， p>

All images are added with a timestamp, obtained by using

time_t unixTime = (time_t) [[NSDate date] timeIntervalSince1970];

等于自1970年以来的秒数的整数

an integer that is equal to the number of seconds since 1970

因此，如何检索核心数据的最后插入的记录（=具有最大时间戳记号的记录）

so, how do I retrieve the last inserted record of a core data (= the record that has the biggest timestamp number)???

谢谢

推荐答案

执行撷取要求，并按 timeStamp / p>

Perform a fetch request, sorting the results by timeStamp.

NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];
[request setEntity:...];

// Results should be in descending order of timeStamp.
NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"timeStamp" ascending:NO];
[request setSortDescriptors:[NSArray arrayWithObject:sortDescriptor]];

NSArray *results = [managedObjectContext executeFetchRequest:request error:NULL];
Entity *latestEntity = [results objectAtIndex:0];

您可能还想使用 NSFetchRequest ' setFetchLimit：。

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