核心数据关系：如何将新对象插入到实体中并创建与另一实体中的现有对象的关系 [英] Core Data Relationships: How to insert a new object into an entity and create a relationship to an existing object in another entity
问题描述
我正在建立一个小小的iPhone应用程式，让使用者保持游戏的分数，他们可能会与朋友一起玩。我现在需要使用Core Data中的关系，但似乎不能使它工作。
我想在一个实体中添加新数据，同时在不同实体中创建与现有数据的关系。如何实现这一点？
请注意，我是Core Data的新用户，并且花了今天最好的一部分，已经用完了运气。任何帮助将非常感激。
我有3个实体：
属性： > date ， player1Score ， player2Score 和状态。 游戏属性： title 。
玩家属性： name 。
我有许多关系（分数< < - > 游戏）和（得分< - >> 玩家）
我已经有一个游戏和玩家的列表。用户选择哪个游戏和正在玩的游戏，并且利用该信息，在 Scores 实体中创建一组对象，该对象具有与所选游戏和玩家的关系。
这是我的来源：
// Scores.h
#import< Foundation / Foundation.h>
#import< CoreData / CoreData.h>
@class游戏，玩家;
@interface评分：NSManagedObject
@property（nonatomic，retain）NSDate * date;
@property（nonatomic，retain）NSNumber * player1Score;
@property（nonatomic，retain）NSNumber * player2Score;
@property（nonatomic，retain）NSNumber * status;
@property（nonatomic，retain）NSSet * game;
@property（nonatomic，retain）NSSet * player;
@end
@interface Scores（CoreDataGeneratedAccessors）
- （void）addGameObject：（Games *）value;
- （void）removeGameObject：（Games *）value;
- （void）addGame：（NSSet *）values;
- （void）removeGame：（NSSet *）values;
- （void）addPlayerObject：（Players *）value;
- （void）removePlayerObject：（Players *）value;
- （void）addPlayer：（NSSet *）values;
- （void）removePlayer：（NSSet *）values;
@end
// SC_ScoreViewController.h
#import< UIKit / UIKit.h>
@interface SC_ScoreViewController：UIViewController
@property（strong）NSIndexPath * game;
@property（strong）NSIndexPath * playerOne;
@property（strong）NSIndexPath * playerTwo;
@property（weak，nonatomic）IBOutlet UILabel * playerOneName;
@property（weak，nonatomic）IBOutlet UILabel * playerTwoName;
@end
// SC_ScoreViewController.m
#importSC_ScoreViewController.h
#importScores.h
#importPlayers.h
#importGames.h
@interface SC_ScoreViewController（）
@end
@implementation SC_ScoreViewController
@synthesize game;
@synthesize playerOne;
@synthesize playerTwo;
// managedObjectContext（context）
- （NSManagedObjectContext *）managedObjectContext {
NSManagedObjectContext * context = nil;
id delegate = [[UIApplication sharedApplication] delegate];
if（[delegate respondingToSelector：@selector（managedObjectContext）]）{
context = [delegate managedObjectContext];
}
return context;
}
- （id）initWithNibName：（NSString *）nibNameOrNil bundle：（NSBundle *）nibBundleOrNil
{
self = [super initWithNibName：nibNameOrNil bundle：nibBundleOrNil ];
if（self）{
//自定义初始化
}
return self;
}
- （void）viewDidLoad
{
[super viewDidLoad];
//设置导航标题
self.navigationItem.title = [self.game valueForKey：@title];
//设置播放器名称
[self.playerOneName setText：[self.playerOne valueForKey：@name]];
[self.playerTwoName setText：[self.playerTwo valueForKey：@name]];
Scores * newEntry = [NSEntityDescription insertNewObjectForEntityForName：@ScoresinManagedObjectContext：self.managedObjectContext];
newEntry.player1Score = 0;
newEntry.player2Score = 0;
newEntry.status = nil;
newEntry.player = self.playerOne; //从NSIndexPath分配给NSSet的指针类型不兼容
NSError * error;
if（！[self.managedObjectContext save：& error]）{
NSLog（@Whoops，could not save：％@，[error localizedDescription]）;
}
- （void）didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
//处理可以重新创建的任何资源。
}
@end
我希望我已经清楚了，并提供了足够的信息。这是我的第一个问题，所以我希望一切顺利。
您必须插入玩家对象插入 self.managedObjectContext 与插入新的 Score 对象完全相同。它可以是这样的：
Scores * score = [NSEntityDescription insertNewObjectForEntityForName：@ScoresinManagedObjectContext：self.managedObjectContext];
Player * player = [NSEntityDescription insertNewObjectForEntityForName：@PlayerinManagedObjectContext：self.managedObjectContext];
[score addPlayerObject：player];
您还必须更改您的关系Scores<< --- >> Players订购，因为现在你不知道哪个播放器是哪个。这里的其他选项是使用两个多对一的关系（分别对player1和player2）。
另一件事：这是一个最佳实践，单数形式，因此 Score ，而不是 Scores 等。
您应该阅读核心数据编程中的关系和获取的属性指南。
更新：我认为游戏之间不应该有多对多的关系和Scores（从我的理解Score可以重命名为Match）。它可能应该是一对多的关系。
I am building a little iPhone app which allows users to keep score of games they may be playing with friends. I now need to use relationships in Core Data but can't quite seem to get it working.
I want to be able to add new data into one entity while creating a relationship to existing data in a different entity. How can I achieve this?
Please note I am new to Core Data and have spent the best part of today trying to figure this out but have run out of luck. Any help would be very much appreciated.
I have 3 entities: Scores, Games and Players.
Scores Attributes: date, player1Score, player2Score and status.
Games Attributes: title.
Players Attributes: name.
I have many to many relationships between (Scores <<--->> Games) and (Scores <<--->> Players)
I already have a list of both games and players. The user selects which game and who is playing and with this information a set of objects is created in the Scores entity with relationships to the chosen game and players.
Here is my source:
// Scores.h
#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>
@class Games, Players;
@interface Scores : NSManagedObject
@property (nonatomic, retain) NSDate * date;
@property (nonatomic, retain) NSNumber * player1Score;
@property (nonatomic, retain) NSNumber * player2Score;
@property (nonatomic, retain) NSNumber * status;
@property (nonatomic, retain) NSSet *game;
@property (nonatomic, retain) NSSet *player;
@end
@interface Scores (CoreDataGeneratedAccessors)
- (void)addGameObject:(Games *)value;
- (void)removeGameObject:(Games *)value;
- (void)addGame:(NSSet *)values;
- (void)removeGame:(NSSet *)values;
- (void)addPlayerObject:(Players *)value;
- (void)removePlayerObject:(Players *)value;
- (void)addPlayer:(NSSet *)values;
- (void)removePlayer:(NSSet *)values;
@end
// SC_ScoreViewController.h
#import <UIKit/UIKit.h>
@interface SC_ScoreViewController : UIViewController
@property (strong) NSIndexPath *game;
@property (strong) NSIndexPath *playerOne;
@property (strong) NSIndexPath *playerTwo;
@property (weak, nonatomic) IBOutlet UILabel *playerOneName;
@property (weak, nonatomic) IBOutlet UILabel *playerTwoName;
@end
// SC_ScoreViewController.m
#import "SC_ScoreViewController.h"
#import "Scores.h"
#import "Players.h"
#import "Games.h"
@interface SC_ScoreViewController ()
@end
@implementation SC_ScoreViewController
@synthesize game;
@synthesize playerOne;
@synthesize playerTwo;
// managedObjectContext (context)
- (NSManagedObjectContext *)managedObjectContext {
NSManagedObjectContext *context = nil;
id delegate = [[UIApplication sharedApplication] delegate];
if ([delegate respondsToSelector:@selector(managedObjectContext)]) {
context = [delegate managedObjectContext];
}
return context;
}
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Setup Nav Title
self.navigationItem.title = [self.game valueForKey:@"title"];
// Setup Player's Names
[self.playerOneName setText:[self.playerOne valueForKey:@"name"]];
[self.playerTwoName setText:[self.playerTwo valueForKey:@"name"]];
Scores * newEntry = [NSEntityDescription insertNewObjectForEntityForName:@"Scores" inManagedObjectContext:self.managedObjectContext];
newEntry.player1Score = 0;
newEntry.player2Score = 0;
newEntry.status = nil;
newEntry.player = self.playerOne; // Incompatible pointer types assigning to NSSet from NSIndexPath
NSError *error;
if (![self.managedObjectContext save:&error]) {
NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
@end
I hope I have been clear and provided enough information. This is my first question so I hope all is in order. Any help would be amazing, thank you.
You have to insert Players' objects into self.managedObjectContext exactly the same as you insert a new Score object. It could be something like this:
Scores *score = [NSEntityDescription insertNewObjectForEntityForName:@"Scores" inManagedObjectContext:self.managedObjectContext];
Player *player = [NSEntityDescription insertNewObjectForEntityForName:@"Player" inManagedObjectContext:self.managedObjectContext];
[score addPlayerObject:player];
You also have to change your relationship "Scores <<--->> Players" to be ordered, because right now you won't know which player is which. Other option here would be to use two many-to-one relationship (separately for player1 and player2).
One more thing: it's a best practice to name your entities in a singular form, so Score, instead of Scores and so on.
You should read Relationships and Fetched Properties in Core Data Programming Guide. It's all nicely described in there.
UPDATE: I think there shouldn't be a many-to-many relationship between Games and Scores (from what I understand Score can be renamed to Match). It probably should be a one-to-many relationship.
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