ios - 核心数据保存实体问题

Question

这可能是一个非常原始的问题。我有一个属于不同国家的州列表。

Data 1: state - xyz
        country - A

Data 2 : state - abc
         country - B

Data 3: state - ght
        country - A

Data 2 : state - ase
         country - B

在核心数据中，我有不同的州和国家实体。在保存时我如何将所有州放入他们的国家对象？

编辑:国家关系

Answer 1

假设数据是字典数组，

for (NSDictionary *data in datas) {

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Country" inManagedObjectContext:[dbManager getCurrentContext]];
    [fetchRequest setEntity:entity];

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name = %@", [data valueForKey:@"country"]];
    [fetchRequest setPredicate:predicate];

    NSError *error;
    NSArray * fetchedObjects = [managedObjectContext executeFetchRequest:fetchRequest error:&error];
    if ([fetchedObjects count] > 0) {

        Country *country = [fetchedObjects objectAtIndex:0];
        //Using CoreDataGeneratedAccessors
        [country addStateObject:[data valueForKey:@"state"]];
    } else {

        Country *country = [NSEntityDescription insertNewObjectForEntityForName:@"Country" inManagedObjectContext:managedObjectContext];
        country.name = [data valueForKey:@"country"];
        ...

        if ([managedObjectContext save:&error])
        {
             //Using CoreDataGeneratedAccessors
             [country addStateObject:[data valueForKey:@"state"]];
        }
    }
}

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