相关疑难解决方法(0)

我Model.xcdatamodeld用一个实体创建了一个iOS项目和一个托管对象模型().在application:didFinishLaunchingWithOptions:我想测试托管对象模型是否存在,但是我得到了nil.在创建托管对象模型后,是否必须执行一些特殊操作才能创建托管对象上下文？

关于我可能做错的任何建议？

这是界面

@interface AppDelegate : UIResponder <UIApplicationDelegate>
{

}

@property (nonatomic, strong, readonly) NSManagedObjectContext *managedObjectContext;
@property (nonatomic, strong, readonly) NSManagedObjectModel *managedObjectModel;
@property (nonatomic, strong, readonly) NSPersistentStoreCoordinator *persistentStoreCoordinator;

@end

这是实现文件

#import "AppDelegate.h"
#import "RootViewController.h"

@implementation AppDelegate

@synthesize window = _window;
@synthesize managedObjectContext = _managedObjectContext;
@synthesize managedObjectModel = _managedObjectModel;
@synthesize persistentStoreCoordinator = _persistentStoreCoordinator;
@synthesize navigationController = _navigationController;


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    if (![self managedObjectContext]) 
    {
        NSLog(@"Does not exist");
    }

    return YES;
}