ios - +entityForName : nil happens intermittently

Question

我有一个使用核心数据的项目，这个错误会间歇性地发生。我知道实体在那里，因为大多数时候，应用程序打开并显示 entityName 的内容。1. 这是在应用程序委托(delegate)中发生的，而不是被 segue'd2. 当我执行 [self.managedObjectModel entities] 时，entityName 在那里但应用程序崩溃3.不拼错。4.它发生在同一个地方，同一个时间(应用程序启动)

NSManagedObjectContext *contOBJ = self.managedObjectContext;
NSEntityDescription *entity;
NSString * entityForNameString = @"MessageLists";
@try {
    entity = [NSEntityDescription entityForName:entityForNameString
                         inManagedObjectContext:contOBJ];
}
@catch (NSException* exception) {
    NSLog(@"DANGER DANGER - ERROR FOUND");
    NSLog(@"Uncaught exception: %@", exception.description);

    // ditch effort to reset manageObject BUT DOES NOT WORK...
    [self.managedObjectContext reset];
    // ditch effort to reset manageObject BUT DOES NOT WORK...

    return nil;
NSLog(@"Stack trace: %@", [exception callStackSymbols]);

    // Reset the store
}
@finally {        
    NSLog(@"finally");
}
NSFetchRequest *fetcher = [[NSFetchRequest alloc] init];
// need to define a predicate that will institute weather a message thread is deleted or NOT
[fetcher setEntity:entity];
NSError *error;
NSLog(@"All Records is %@",[contOBJ executeFetchRequest:fetcher error:&error]);
return [contOBJ executeFetchRequest:fetcher error:&error];

Answer 1

不要使用那些旧的字符串类型的东西，就这样做

NSFetchRequest *fetchRequest = [MessageLists fetchRequest];
NSError *error;
NSLog(@"All Records is %@",[context executeFetchRequest:fetchRequest error:&error]);