iphone - CoreData 无法保存上下文，表示关系为零 - 但它肯定已设置

Question

当我尝试保存 CoreData 模型的上下文时，收到错误


Unresolved error Error Domain=NSCocoaErrorDomain Code=1560 "The operation couldn’t be completed. (Cocoa error 1560.)" UserInfo=0x76924b0 {NSDetailedErrors=(
"Error Domain=NSCocoaErrorDomain Code=1570 "
The operation couldn\U2019t be completed. (Cocoa error 1570.)"
UserInfo=0x768c410 {NSValidationErrorObject=<Posts: 0x7177990> (entity: Posts; id: 0x7177010 <x-coredata:///Posts/tEF7138E6-A968-45B7-95CF-116C2AA93D605> ; data: {\n "
business_entity"
= nil;\n "<br/>
created_at"
= "
2012-01-21 03:31:30 +0000"
;\n "
own_description"
= "
Roasted this morning- Panama Duncan Estate: A rose fragrance debuts flavors of pear, coconut and marshmallow with caramel throughout the cup."
;\n postsID = 4;\n "
updated_at"
= "
2012-01-21 03:31:30 +0000"
;\n}), NSValidationErrorKey=business_entity, NSLocalizedDescription=The operation couldn\U2019t be completed. (Cocoa error 1570.)}",


关键部分是:

business_entity = nil;<br/>
NSValidationErrorKey=business_entity


但是，当我创建“Posts”对象时，我将它们设置为:

    // First try to find a business for the post
NSNumber* businessID = [NSNumber numberWithInteger: [(NSString*)[jsonInfo objectForKey:@"business_id"] integerValue]];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
[fetchRequest setEntity: [NSEntityDescription entityForName:kCoreDataModelNameBusinesses inManagedObjectContext: self.managedObjectContext]];
[fetchRequest setPredicate: [NSPredicate predicateWithFormat:@"(businessesID == %i)", [businessID intValue]]];

NSError *error = nil;
NSArray *matchingManagedObjects = [__managedObjectContext executeFetchRequest:fetchRequest error:&error];

if(error) {
    NSLog(@"Error-createNewPostsWithJsonInfo: Unresolved error %@, %@", error, [error userInfo] );
    return;
}

// Check any results
if( [matchingManagedObjects count] == 0) {
    NSLog(@"Error-createNewPostsWithJsonInfo: Could not locate a matching businessId: %@ for postId:%@", businessID, (NSString*)[jsonInfo objectForKey:@"id"]);
}
// Check too many results    
if( [matchingManagedObjects count] > 1) {
    NSLog(@"Error-createNewPostsWithJsonInfo: Too many bussinesses match businessId: %@ for postId:%@", businessID, (NSString*)[jsonInfo objectForKey:@"id"]);
}

// Final sanity check outputs fine!!
NSLog(@"Business entity %@", (Businesses*)[matchingManagedObjects objectAtIndex:0] );

// Finally create the post 
Posts* newPosts = [NSEntityDescription
                           insertNewObjectForEntityForName:entityName inManagedObjectContext:self.managedObjectContext];

newPosts.created_at = [_dateFormater dateFromString: [jsonInfo objectForKey:@"created_at"] ];
newPosts.updated_at = [_dateFormater dateFromString: [jsonInfo objectForKey:@"updated_at"] ];
newPosts.own_description = [jsonInfo objectForKey:@"description"];
newPosts.postsID = [NSNumber numberWithInteger: [(NSString*)[jsonInfo objectForKey:@"id"] integerValue]];
[newPosts setBusiness_entity: (Businesses*)[matchingManagedObjects objectAtIndex:0] ];

所以我知道 Business_entity 正在设置，并且是正确的。在这种情况下，什么会导致它在保存上下文时出错？

如果有帮助的话，这是模型:

Answer 1

万一有人遇到这个问题，错误在于我在 coredatamodel 中设置关系的方式。

这些图像将比我更好地解释，但请确保您在所有者实体中将关系设置为多对多，否则它不会为您动态创建可变集