ios – 获取一对多关系数据的核心数据

INSERT INTO Routine (Values) WHERE Routine.userID = user.usersExercise

是的,您需要使用NSPredicate来获取与特定用户相关的数据.如果您正在填充UICollection视图,那么我建议您也阅读NSFetchedResultsController.

NSFetchRequest *fetchRequestItems = [[NSFetchRequest alloc] init];
NSEntityDescription *entityItem = [NSEntityDescription entityForName:@"Routine" inManagedObjectContext:self.managedObjectContext];
[fetchRequestItems setEntity:entityItem];

User* myUser = //Code for getting current user out of data store based on some paramator
[fetchRequestItems setPredicate:[NSPredicate predicateWithFormat:@"userID == %@",myUser]];

//Sort by last edit ordered
NSArray *sortDescriptors = [NSArray arrayWithObjects:nil];
[fetchRequestItems setSortDescriptors:sortDescriptors];

NSArray* Routines = [managedObjectContext executeFetchRequest:fetchRequest error:&error];

这里需要注意的是,您需要在Routine / Exercise对象上设置反向关系,以与谓词中的当前用户进行比较.对于我认为是反向关系的userID你有哪些？

所以从评论中我没有设置反比关系所以这里是一个粗略的例子.

在您的商店中制作新用户时,您会得到这样的信号：

User *thisUser = [NSEntityDescription insertNewObjectForEntityForName:@"User" inManagedObjectContext:self.managedObjectContext];

thisUser.eMail = emailAddress.text;
//And any other paras you might have

然后在为该用户创建例程时,您将执行以下操作：

Routine *newRoutine = [NSEntityDescription insertNewObjectForEntityForName:@"Routine" inManagedObjectContext:managedObjectContext];

newRoutine.userId = thisUser;

然后确保保存托管对象以将更改写入数据存储.然后,它将例程侧的2个对象链接起来,不要忘记在用户端链接它以获得严格的反向关系.

为了让用户完全像我上面提到的那样：

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"User" inManagedObjectContext:managedObjectContext];
[fetchRequest setEntity:entity];

NSError* error;
NSArray* Users = [managedObjectContext executeFetchRequest:fetchRequest error:&error];

如果你有1个用户,那么它是数组中的第一个元素,如果你有很多用户,那么使用谓词根据你的FB id找到一个.