iOS CoreData 开发之数据模型关系

 1 - (void)insertToDB:(NSString *)username password:(NSString *)password
 2 {
 3     User *u = (User *)[NSEntityDescription insertNewObjectForEntityForName:@"User" inManagedObjectContext:self.cdContext];
 4     u.username = username;
 5     u.password = password;
 6     
 7     UserInfo *info = (UserInfo *)[NSEntityDescription insertNewObjectForEntityForName:@"UserInfo" inManagedObjectContext:self.cdContext];
 8     info.age = @12;
 9     info.sex = @1;
10     info.address = @"中国";
11     
12     u.userInfo = info;
13     info.user = u;
14     
15     
16     NSError *err;
17     if(![self.cdContext save:&err])
18     {
19         NSLog(@"Error %@  %@",err.localizedDescription,err.localizedFailureReason);
20     }
21 
22 }
23 
24 - (void)readFromDb
25 {
26     NSFetchRequest *fetch = [[NSFetchRequest alloc] init];
27     NSEntityDescription *entity = [NSEntityDescription entityForName:@"User" inManagedObjectContext:self.cdContext];
28     [fetch setEntity:entity];
29     //限制只取1条
30     [fetch setFetchLimit:1];
31     NSError* err;
32     NSArray *results = [self.cdContext executeFetchRequest:fetch error:&err];
33     if(err)
34     {
35         NSLog(@"Error %@  %@",err.localizedDescription,err.localizedFailureReason);
36         return;
37     }
38     [results enumerateObjectsUsingBlock:^(User  *_Nonnull user, NSUInteger idx, BOOL * _Nonnull stop) {
39         NSLog(@"----username:%@  password:%@ address:%@",user.username,user.password,user.userInfo.address);
40     }];
41 }