ios - 尝试访问核心数据时出错

我正在尝试获取我保存在一个核心数据对象中的值，但是我不断收到此错误

 *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '+entityForName: nil is not a legal NSManagedObjectContext parameter searching for entity name 'Man''

结果错误发生在我编写的代码中，它尝试访问核心数据对象然后记录其内容，如下所示。

if ([manufDBVNumber isEqualToNumber:currentDBVersion]) {
        // READ FROM CORE DATA
        // WRITE TO CORE DATA
        NSManagedObjectContext *context = [self managedObjectContext];

        NSLog(@"%@", context);

        // Test listing all FailedBankInfos from the store
        NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
        NSEntityDescription *entity = [NSEntityDescription entityForName"Man" inManagedObjectContext:self.managedObjectContext]; // This is where the error is happening.
        [fetchRequest setEntity:entity];

        NSError *error;


        NSMutableArray *manufacturerDictionaryArray = [[NSMutableArray alloc] init];


        NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:&error];
        for (Manuf *manuf in fetchedObjects) {
            NSLog(@"MANA: %@", man.mana);
            NSLog(@"SURGE: %@", man.surge);
            NSLog(@"HEALTH: %@", manuf.health);


etc//....

这就是我合成 managedObjectContext 和 fetchedResultsController 的方式

// Core-Data variables used for fetching and managing the object
@synthesize fetchedResultsController = __fetchedResultsController;
@synthesize managedObjectContext = __managedObjectContext;

任何帮助将不胜感激。

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Best Answer-推荐答案

你这样做:

NSManagedObjectContext *context = [self managedObjectContext];

然后你访问这个:

self.managedObjectContext

假设你的 NSLog(@"%@", context); 显示一个有效的 NSManagedObjectContext，那么我会这样做:

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

或者，将您的原始声明更改为:

self.managedObjectContext = [self managedObjectContext];

关于ios - 尝试访问核心数据时出错，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/12666919/