我是核心数据的新手,因此我有几个问题。我会问两个核心数据插入和获取多对多关系实体
1)我有两个实体名为Team和TeamMembers。他们有多对多的关系,即一个团队可以有很多成员。首先请看下面的模型图和.h文件,并让我知道我是否已经在Team和TeamMembers之间建立了正确的一对多关系(我有一种感觉,我已经建立了相反的关系)。
Teams.h
#import <CoreData/CoreData.h>
@class TeamMembers;
@interface Teams : NSManagedObject
{
}
@property (nonatomic, retain) NSString * team_name;
@property (nonatomic, retain) NSString * color;
@property (nonatomic, retain) NSString * points;
@property (nonatomic, retain) TeamMembers * members;
@end
TeamMembers.h
#import <CoreData/CoreData.h>
@class Teams;
@interface TeamMembers : NSManagedObject
{
}
@property (nonatomic, retain) NSString * member_name;
@property (nonatomic, retain) NSSet* teams;
@end
@interface TeamMembers (CoreDataGeneratedAccessors)
- (void)addTeamsObject:(Teams *)value;
- (void)removeTeamsObject:(Teams *)value;
- (void)addTeams:(NSSet *)value;
- (void)removeTeams:(NSSet *)value;
@end
2)请我需要的示例代码插入小组随后将其团队成员。另外如何获取特定团队的团队成员。
EDITED 我使用下面的代码插入到团队和团队成员的实体,但它没有返回在NSSet中所有团队成员。它只返回结果集中的一个团队成员
self.context = [del managedObjectContext];
Teams *teamobj = [NSEntityDescription
insertNewObjectForEntityForName:@"Teams"
inManagedObjectContext:context];
teamobj.team_name = teamname.text;
teamobj.color = [NSString stringWithFormat:@"%d", color];
teamobj.points = [NSString stringWithFormat:@"%d", 0];
for(UITextField *view in self.scrollview.subviews)
{
if([view isKindOfClass:[UITextField class]])
{
if ([view tag] == 99) {
if (![view.text isEqualToString:@""]) {
noone = YES;
TeamMembers *teammember = [NSEntityDescription
insertNewObjectForEntityForName:@"TeamMembers"
inManagedObjectContext:context];
teammember.member_name = view.text;
teammember.teams = teamobj;
[teamobj addMembersObject:teammember];
}
}
}
}
if (![context save:&error]) {
NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Failure" message:@"Unable to save team at the moment." delegate:self cancelButtonTitle:@"ok" otherButtonTitles:nil];
[alert show];
[alert release];
}
感谢您的答复。你能否给出一个在TeamMembers中为特定团队插入的示例 –
也可以将你的实体命名为单数对象而不是复数;所以'团队'和'团队成员',而不是'团队'和'团队成员'。 –
感谢您展示示例代码。你是否也可以展示如何将NSSet团队成员添加到团队中? –