ios - executefetchrequest 导致崩溃

Question

我正在尝试在 iOS 7 应用程序中实现 Core Data(并且之前已成功完成)。但是，当我执行executeFetchRequest 方法时，应用程序崩溃了。下面添加了最相关的代码:

#import "JTHuntingSeasonDB.h"

@implementation JTHuntingSeasonDB

- (id)init {
    self = [super init];
    if (self) {
        NSFileManager *fileManager = [NSFileManager defaultManager];
        NSURL *documentsDirectory = [[fileManager URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] firstObject];

        NSString *documentName = @"JTHuntingDB";
        NSURL *url = [documentsDirectory URLByAppendingPathComponent:documentName];

        document = [[UIManagedDocument alloc] initWithFileURL:url];


        BOOL fileExists  = [[NSFileManager defaultManager] fileExistsAtPath:[url path]];

        if (fileExists) {
            [document openWithCompletionHandler:^(BOOL success) {
                if (success) {
                    NSLog(@"Document opened successfully");
                    self.allSpecies = [self getSpecies];
                    self.speciesToday = [self getSpeciesToday];
                } else NSLog(@"Failed to open document");
            }];
        } else {
            [document saveToURL:url forSaveOperation:UIDocumentSaveForCreating completionHandler:^(BOOL success) {
                if (success)  {
                    NSLog(@"Document created successfully");
                    self.allSpecies = [self getSpecies];
                    self.speciesToday = [self getSpeciesToday];
                }  else NSLog(@"Failed to create document, path: %@", url);
            }];
        }
    }

    return self;
}

#pragma mark - Core Data

- (NSArray *)getSpecies {
    if (document.documentState == UIDocumentStateNormal) {
        context = document.managedObjectContext;

        NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
        NSString *country = [defaults stringForKey:@"Country"];
        NSString *subregion = [defaults stringForKey:@"Subregion"];

        NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"HuntingDates"];
        NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"name" ascending:YES selector:@selector(localizedStandardCompare:)];
        request.fetchBatchSize = 150;
        request.fetchLimit = 150;
        request.sortDescriptors = @[sortDescriptor];

        if (subregion.length > 0) {
            request.predicate = [NSPredicate predicateWithFormat:@"(country IN %@) AND (subregion IN %@)", country, subregion];
        } else {
            request.predicate = [NSPredicate predicateWithFormat:@"country IN %@", country];
        }

        NSError *error;
        return [context executeFetchRequest:request error:&error];
    }

    return nil;
}

线路

return [context executeFetchRequest:request error:&error];

导致应用程序崩溃。这是我迄今为止所做和发现的:

• 模拟器:已删除应用并重置内容和设置
• Xcode:清理(构建文件夹)
• “上下文”不为零
• NSLog 打印出“文档已创建/打开成功”
• 当应用程序崩溃时，控制台中只会打印“lldb”

编辑:在听从 Wain 的建议后，我关闭了异常断点，得到了一条更具描述性的错误消息，指出谓词无效。通过用 CONTAINS 替换谓词中的 IN 并更改变量“country”以使其不再返回 nil 来解决问题。

Answer 1

我猜这是你的谓词，因为 IN 是一个集合运算符，但你传递的是字符串(应该是数组/集合)。

如果您使用字符串，则应在谓词中使用 CONTAINS。