用于根据相关数据进行筛选的iOS核心数据谓词

好吧，我是个傻瓜。他们对我来说是陌生的

关于应用程序： 我有一个处理游戏比赛的应用程序。有球员、签到和比赛的实体。 这样做的目的是将玩家添加到应用程序中，然后可以登录进行比赛，并存储比赛结果

关系： 玩家>签入（每个玩家可以在不同日期有多个签入）

• 发件人：玩家实体
• 关系：playerCheckins
• 反向：棋盘手
• 目的地：签入实体

球员比赛（每场比赛可以有两名球员，球员在每次比赛中可以有多场比赛）

• 发件人：玩家实体
• 关系：playerMatches
• 反向：棋手
• 目标：匹配实体

我有一个共享的集合视图，其中列出了应用程序中的所有玩家。当玩家签入和添加到新的比赛条目时使用。到目前为止，所有这些都很有效

我想做的是： 我希望玩家集合视图根据他们的签入状态筛选列出的玩家。例如，签入新玩家时，“玩家集合”视图应仅显示当天尚未签入的玩家。（签入每个条目都有一个日期属性）此外，当向比赛中添加球员时，集合视图应仅显示当天已签入的球员

我正计划向players集合视图添加一个NSString属性，该属性是在以模式加载集合视图时使用谓词文本设置的。这样，我可以根据是否分别从匹配视图和签入视图调用集合视图来更改谓词

这是可能的，我正在尝试做什么？这些谓词字符串是什么样子的

谢谢

更新 我应该更清楚。我正在使用一个fetchedresultscontroller让玩家进入collectionview，所以我正在寻找一个谓词来在fetch请求中使用

正在添加代码。。。 My CollectionViewController：

PlayersCollectionViewController.h
#import "CoreCollectionViewController.h"
#import "Player.h"

@protocol PlayersCollectionViewControllerDelegate;


@interface PlayersCollectionViewController : CoreCollectionViewController <NSFetchedResultsControllerDelegate>

@property (nonatomic, assign) id <PlayersCollectionViewControllerDelegate> delegate;
@property (nonatomic, strong) NSString *titleText;
@property (nonatomic, strong) NSString *predicate;

- (IBAction)cancel:(UIBarButtonItem *)sender;
- (IBAction)done:(UIBarButtonItem *)sender;

@end

@protocol PlayersCollectionViewControllerDelegate <NSObject>

@optional
-(void)ViewController:(UIViewController *)sender
     didSelectPlayer:(Player *)selectedPlayer;

@optional
-(void)ViewController:(UIViewController *)sender
      didSelectPlayer1:(Player *)selectedPlayer1;

@optional
-(void)ViewController:(UIViewController *)sender
      didSelectPlayer2:(Player *)selectedPlayer2;

@end

playerCollectionViewController.h
#导入“CoreCollectionViewController.h”
#导入“Player.h”
@协议播放器集合视图控制器远程门；
@界面播放器CollectionViewController:CoreCollectionViewController
@属性（非原子，赋值）id委托；
@属性（非原子，强）NSString*titleText；
@属性（非原子，强）NSString*谓词；
-（iAction）取消：（UIBarButtonItem*）发送方；
-（IBAction）完成：（UIBarButtonItem*）发送方；
@结束
@协议播放机集合ViewControllerDelegate
@可选的
-（void）ViewController:（UIViewController*）发送方
didSelectPlayer:（Player*）selectedPlayer；
@可选的
-（void）ViewController:（UIViewController*）发送方
didSelectPlayer1:（播放器*）selectedPlayer1；
@可选的
-（void）ViewController:（UIViewController*）发送方
didSelectPlayer2:（播放器*）selectedPlayer2；
@结束

……以及执行：

#import "PlayersCollectionViewController.h"
#import "AppDelegate.h"
#import "PlayerCollectionViewCell.h"

@interface PlayersCollectionViewController ()
@property(nonatomic, strong) NSManagedObjectContext *managedObjectContext;
@property (nonatomic, strong) NSFetchedResultsController *fetchedResultsController;
@end

@implementation PlayersCollectionViewController
@synthesize titleText, predicate;

static NSString * const reuseIdentifier = @"Cell";

- (instancetype)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

-(NSManagedObjectContext*)managedObjectContext{
    return [(AppDelegate*)[[UIApplication sharedApplication]delegate]managedObjectContext];
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    // Uncomment the following line to preserve selection between presentations
    // self.clearsSelectionOnViewWillAppear = NO;

    // Register cell classes
    [self.collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:reuseIdentifier];

    // Do any additional setup after loading the view.
    NSError *error = nil;
    if (![[self fetchedResultsController]performFetch:&error]) {
        NSLog(@"Error: %@", error);
        abort();
    }
}

-(void)viewWillAppear:(BOOL)animated
{
    [self setTitle:titleText];
    [self.collectionView reloadData];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

/*
#pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.
}
*/

#pragma mark <UICollectionViewDataSource>

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
    return [[self.fetchedResultsController sections]count];
}


- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return [[self.fetchedResultsController fetchedObjects]count];
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{

    PlayerCollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"PlayerCollCell" forIndexPath:indexPath];
    Player *player = [self.fetchedResultsController objectAtIndexPath:indexPath];

    // Configure the cell

    if (player.playerImage) {
        cell.playerImageView.image = [UIImage imageWithContentsOfFile:player.playerImageSmall];
    }

    [cell.playerNameLabel setText:player.firstName];

    return cell;
}

-(BOOL)collectionView:(UICollectionView *)collectionView shouldHighlightItemAtIndexPath:(NSIndexPath *)indexPath
{
    return YES;
}

-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{

    PlayerCollectionViewCell *selectedPlayerCell = (PlayerCollectionViewCell*)[collectionView cellForItemAtIndexPath:indexPath];

    [collectionView dequeueReusableCellWithReuseIdentifier:@"PlayerCollCell" forIndexPath:indexPath];

    selectedPlayerCell.backgroundColor = [UIColor lightGrayColor];

    Player *selectedPlayer = [self.fetchedResultsController objectAtIndexPath:indexPath];

    NSLog(@"Selected player %@", selectedPlayer.firstName);

    if ([self.title isEqualToString:@"Select Player 1"]) {
        [self.delegate ViewController:self didSelectPlayer1:selectedPlayer];
    } else if ([self.title isEqualToString:@"Select Player 2"]) {
        [self.delegate ViewController:self didSelectPlayer2:selectedPlayer];
    } else if ([self.title isEqualToString:@"Select Player"]) {
        [self.delegate ViewController:self didSelectPlayer:selectedPlayer];
    }

    [self dismissViewControllerAnimated:YES completion:nil];
}

#pragma mark - ViewController methods
- (IBAction)cancel:(UIBarButtonItem *)sender {
    [self dismissViewControllerAnimated:YES completion:nil];
}

- (IBAction)done:(UIBarButtonItem *)sender { //not sure if this method and UI are needed...
    [self dismissViewControllerAnimated:YES completion:nil];
}


#pragma mark - Fetched Results Controller Section
-(NSFetchedResultsController*) fetchedResultsController
{
    if (_fetchedResultsController !=nil) {
        return _fetchedResultsController;
    }

    NSFetchRequest *fetchedRequest = [[NSFetchRequest alloc]init];

    NSManagedObjectContext *context = [self managedObjectContext];

    NSEntityDescription *entity =[NSEntityDescription entityForName:@"Player" inManagedObjectContext:context];

    [fetchedRequest setEntity:entity];

    NSSortDescriptor *lastNameSortDescriptor = [[NSSortDescriptor alloc]initWithKey:@"lastName" ascending:YES];
    NSSortDescriptor *firsttNameSortDescriptor = [[NSSortDescriptor alloc]initWithKey:@"firstName" ascending:YES];

    NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:lastNameSortDescriptor, firsttNameSortDescriptor, nil];

    fetchedRequest.sortDescriptors = sortDescriptors;


    _fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchedRequest
                                                                    managedObjectContext:context
                                                                      sectionNameKeyPath:nil
                                                                               cacheName:nil];

    _fetchedResultsController.delegate = self;

    return _fetchedResultsController;

}

#pragma mark - Fetched Results Controller Delegates
/*
 -(void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
 [self.collectionView beginUpdates];
 }

 -(void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
 [self.collectionView endUpdates];
 }
 */

-(void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath {

    UICollectionView *collectionView = self.collectionView;

    switch (type) {
        case NSFetchedResultsChangeInsert:
            [collectionView insertItemsAtIndexPaths:[NSArray arrayWithObjects:newIndexPath, nil]];
            break;

        case NSFetchedResultsChangeDelete: [collectionView deleteItemsAtIndexPaths:[NSArray arrayWithObjects:indexPath, nil]];
            break;

        case NSFetchedResultsChangeUpdate: {
            PlayerCollectionViewCell *selectedPlayerCell = (PlayerCollectionViewCell*)[collectionView cellForItemAtIndexPath:indexPath];

            //selectedPlayerCell.backgroundColor = [UIColor lightGrayColor];

            Player *selectedPlayer = [self.fetchedResultsController objectAtIndexPath:indexPath];

            if (selectedPlayer.playerImage) {
                selectedPlayerCell.playerImageView.image = [UIImage imageWithContentsOfFile:selectedPlayer.playerImageSmall];
            }

            [selectedPlayerCell.playerNameLabel setText:selectedPlayer.firstName];

        }
            break;

        case NSFetchedResultsChangeMove: [collectionView deleteItemsAtIndexPaths:[NSArray arrayWithObjects:indexPath, nil]];
            [collectionView insertItemsAtIndexPaths:[NSArray arrayWithObjects:newIndexPath, nil]];
            break;

    }

}

@end

#导入“playerCollectionViewController.h”
#导入“AppDelegate.h”
#导入“PlayerCollectionViewCell.h”
@界面播放器集合视图控制器（）
@属性（非原子，强）NSManagedObjectContext*managedObjectContext；
@属性（非原子，强）NSFetchedResultsController*fetchedResultsController；
@结束
@PlayerCollectionViewController的实现
@综合titleText、谓词；
静态NSString*const reuseIdentifier=@“Cell”；
-（instancetype）initWithNibName:（NSString*）nibNameOrNil bundle:（NSBundle*）nibBundleOrNil
{
self=[super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]；
如果（自我）{
//自定义初始化
}
回归自我；
}
-（NSManagedObjectContext*）managedObjectContext{
返回[（AppDelegate*）[[UIApplication sharedApplication]委托]managedObjectContext]；
}
-（无效）viewDidLoad
{
[超级视图下载]；
//取消注释下一行以保留演示文稿之间的选择
//self.clearselectiononviewwillappear=否；
//注册单元类
[self.collectionView注册表类：[UICollectionViewCell类]forCellWithReuseIdentifier:reuseIdentifier]；
//加载视图后执行任何其他设置。
n错误*错误=nil；
如果（！[[self-fetchedResultsController]性能检测：&错误]）{
NSLog（@“错误：%@”，错误）；
中止（）；
}
}
-（无效）视图将显示：（BOOL）动画
{
[自我设置标题：标题文本]；
[self.collectionView-reloadData]；
}
-（无效）未收到记忆警告
{
[超级记忆警告]；
//处置所有可以重新创建的资源。
}
/*
#pragma标记-导航
//在基于故事板的应用程序中，您通常需要在导航之前做一些准备
-（void）prepareForSegue:（UIStoryboardSegue*）segue发送方：（id）发送方
{
//使用[segue destinationViewController]获取新的视图控制器。
//将选定对象传递给新的视图控制器。
}
*/
#布拉格标记
-（NSInteger）collectionView中的节数：（UICollectionView*）collectionView
{
返回[[self.fetchedResultsController节]计数]；
}
-（NSInteger）collectionView:（UICollectionView*）collectionView项目编号截面：（NSInteger）截面
{
返回[[self.fetchedResultsController fetchedObject]计数]；
}
-（UICollectionViewCell*）collectionView:（UICollectionView*）collectionView cellForItemAtIndexPath:（NSIndexPath*）indexPath
{
PlayerCollectionViewCell*cell=[collectionView dequeueReusableCellWithReuseIdentifier:@“PlayerCollectionCell”forIndexPath:indexPath]；
Player*Player=[self.fetchedResultsController对象索引路径：indexPath]；
//配置单元格
if（player.playerImage）{
cell.playerImageView.image=[UIImage-imageWithContentsOfFile:player.playerImageSmall]；
}
[cell.playerNameLabel setText:player.firstName]；
返回单元；
}
-（BOOL）collectionView:（UICollectionView*）collectionView应高亮度项索引路径：（NSI）
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"checkedInStatus == 1"];