iOS 7 CoreData中的大容量更新数据

Question

是否有办法通过一个SQL-查询运行某个实体的所有对象的更新？不是去取和跑-循环。

例如，喜欢运行

UPDATE someEntity SET filed1 = value1 WHERE field2 = value2

Answer 1

Mercelo的答案在iOS-7中是行不通的，你可以

NSFetchRequest *fetchAllRSSItems = [NSFetchRequest fetchRequestWithEntityName:[RSSItem entityName]];
NSError *fetchError;
NSArray *results = [self.managedObjectContext executeFetchRequest:fetchAllRSSItems error:&fetchError];

if (results == nil) {

    NSLog(@"Error: %@", [fetchError localizedDescription]);
} else {

    for (RSSItem *rssItem in results) {
        rssItem.read = [NSNumber numberWithBool:YES];
    }

    [self saveManagedObjectContext];
}

Answer 2

在iOS 8上引入了核心数据批处理更新：

NSBatchUpdateRequest *batchRequest = [NSBatchUpdateRequest batchUpdateRequestWithEntityName:   [RSSItem entityName]];
batchRequest.propertiesToUpdate = @{NSStringFromSelector(@selector(read)): @YES};
batchRequest.resultType = NSStatusOnlyResultType; // NSStatusOnlyResultType is the default
batchRequest.affectedStores = @[...]; // Optional, stores this request should be sent to
batchRequest.predicate = [NSPredicate predicateWithFormat:@"..."]; // Optional, same type of predicate you use on NSFetchRequest

NSError *requestError;
NSBatchUpdateResult *result = (NSBatchUpdateResult *)[self.managedObjectContext executeRequest:batchRequest error:&requestError];

if (result) {
    // Batch update succeeded
} else {
    NSLog(@"Error: %@", [requestError localizedDescription]);
}

但是，它不更改上下文：它直接更改持久存储。这意味着不需要进行验证，之后需要更新UI。

这个答案是基于马修·莫雷的这篇文章的。