核心数据NSFetchRequest setResultType：NSDictionaryResultType不工作 [英] Core Data NSFetchRequest setResultType:NSDictionaryResultType not working

问题描述

将NSFetchRequest结果类型设置为NSDictinaryResultType时，将返回零个对象。如果我删除setPropertiesToFetch和setResultType，则返回所有对象。

When setting a NSFetchRequest result type to NSDictinaryResultType, zero objects are returned. If I remove setPropertiesToFetch and setResultType, all the objects are returned.

任何想法？

NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Alert" inManagedObjectContext:_managedObjectContext];
[request setEntity:entity];

NSDictionary *entityProperties = [entity propertiesByName]; 
[request setPropertiesToFetch:[NSArray arrayWithObject:[entityProperties objectForKey:@"test"]]];
[request setResultType:NSDictionaryResultType];

NSError *error;
NSArray *result = [_managedObjectContext executeFetchRequest:request error:&error];

if (result == nil) {
    NSLog(@"Error: %@", [error localizedDescription]);
}

推荐答案

在插入新对象后保存mangedObjectContext。一旦我这样做，我得到的结果，我在寻找。

The problem was I needed to save the mangedObjectContext after inserting new objects. Once I did that I get the results I was looking for.

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