Question

从核心数据中提取对象时，我将NSFetchRequest结果类型设置为NSDictionaryResultType。设置NSDictionaryResultType时，关系对象不在结果字典中。这段代码可能存在什么问题。如果NSDictionaryResultType不起作用，我将如何获取关系对象？

// get manageObjectContext
AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context = [appDelegate managedObjectContext];

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"SomeName"
                                          inManagedObjectContext:context];
[fetchRequest setEntity:entity];
fetchRequest.relationshipKeyPathsForPrefetching = [NSArray arrayWithObjects:@"anEntity", nil];
[fetchRequest setResultType:NSDictionaryResultType];

fetchRequest.predicate = [NSPredicate predicateWithFormat:@"%K IN %@", @"anId", anArray];

NSError *error;
NSArray *existingTopics = [context executeFetchRequest:fetchRequest error:&error];
fetchRequest = nil;

谢谢！

Answer 1

您需要设置属性propertiesToFetch。查看当前找到的NSFetchRequest NSMutableArray *mutableResults = [results mutableCopy]; for (NSUInteger i = 0; i < mutableResults.count; i++) { NSDictionary *result = mutableResults[i]; // Do a similar fetch for the related objects, returning dictionary // representations. Repeat as necessary for each 1toMany relationship. NSArray *objectsFor1toManyRelationship = [self fetchRelationShipFor:result[@"identifier"]]; NSMutableDictionary *mutableResult = [result mutableCopy]; mutableResult[@"1toManyRelationship"] = objectsFor1toManyRelationship; mutableResults[i] = [mutableResult copy]; }的课程参考。

注意：此属性不适用于一对多（或多对多）关系。

对于此类关系，必须手动添加相关对象。

<强>的伪代码：

Spoon.screenshot(context,fileName)

NSDictionaryResultType不提取关系中的对象 - 核心数据

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