如何在核心数据中插入和获取一对多关系实体

Question

请问我需要一个示例代码，了解如何在一对多关系中保存和获取数据？这是我的两个NSManagedObject子类。我设法保存并获取一对一的关系。

Answer 1

数据保存代码

UserDefinedInterests *aAserDefineInterrest1 = [NSEntityDescription insertNewObjectForEntityForName:@"UserDefinedInterests" inManagedObjectContext:context]; 

aAserDefineInterrest1.name = @"PPP"; 
aAserDefineInterrest1.categoryId = [NSNumber numberWithInt:168004]; 

UserDefinedInterests *aAserDefineInterrest2 = [NSEntityDescription insertNewObjectForEntityForName:@"UserDefinedInterests" inManagedObjectContext:context]; 

aAserDefineInterrest2.name = @"QQQ"; 
aAserDefineInterrest2.categoryId = [NSNumber numberWithInt:12248004]; 

UserDefinedInterests *aAserDefineInterrest3 = [NSEntityDescription insertNewObjectForEntityForName:@"UserDefinedInterests" inManagedObjectContext:context]; 

aAserDefineInterrest3.name = @"RRR"; 
aAserDefineInterrest3.categoryId = [NSNumber numberWithInt:3534535]; 

NSMutableSet *userDefineInterests = [NSMutableSet setWithObjects:aAserDefineInterrest, nil]; 

[aTopic addUserDefinedInterests:userDefineInterests]; 

数据获取代码

// Test listing topic details from the store 
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; 
NSEntityDescription *entity = [NSEntityDescription entityForName:@"SomeEntity" 
              inManagedObjectContext:context]; 
[fetchRequest setEntity:entity]; 

NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:&error]; 
for (TopicDetails *aTopic in fetchedObjects) { 

    ...... 

    NSSet *pp = aTopic.userDefinedInterests; 

    for (some *somearray in pp.allObjects) { 


    } 
}