以下代码中的错误是什么？

Question

我是iOS的初学者.当我将Core Data用于我的示例项目时,它给了我一个线程错误.

请帮我解决这个错误.

这是我的代码:

-(NSFetchedResultsController*)fetchedResultController{
if (self.fetchedResultController != nil ) {
    return self.fetchedResultController;
}

NSFetchRequest *request = [[NSFetchRequest alloc]init];
NSManagedObjectContext *context = [self managedObjectContext];

NSEntityDescription *entity = [NSEntityDescription insertNewObjectForEntityForName:@"Recepie" inManagedObjectContext:context];

[request setEntity:entity];

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc]initWithKey:@"recepieName" ascending:YES];

NSArray *sortDescriptorArray = [[NSArray alloc]initWithObjects:sortDescriptor,nil];

request.sortDescriptors = sortDescriptorArray;

self.fetchedResultController = [[NSFetchedResultsController alloc] initWithFetchRequest: request managedObjectContext:context sectionNameKeyPath:nil cacheName:nil];

self.fetchedResultController.delegate = self;

return self.fetchedResultController;

}

Answer 1

使用这样的点表示法引用属性时

if (self.fetchedResultController != nil ) {
    return self.fetchedResultController;
}

它相当于调用[self fetchedResultController]方法(这是该属性的getter).当你这样做,你已经是 getter中,因此该方法无限自称,导致堆栈溢出错误.

您不应该使用点符号来获取属性值(使用setter是正常的).改为使用支持变量:

if(_fetchedResultController != nil) {
    return _fetchedResultController;
}