无法弄清楚如何重写以下方法swift 为了更好的学习曲线,所以我试着翻译这段代码。所以让我们选择一个更困难的方法来做到这一点。它有error handling
,object init
和parameter settings
,一个array of object pointers
,selectors
,nil
,并self
..如何NSFetchedResultsController编码在Swift
的Objective-C:
-(NSFetchedResultsController *)fetchedResultsController
{
if (_fetchedResultsController != nil) {
return _fetchedResultsController;
}
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
[fetchRequest setFetchBatchSize:20];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"timeStamp" ascending:NO];
NSArray *sortDescriptors = @[sortDescriptor];
[fetchRequest setSortDescriptors:sortDescriptors];
NSFetchedResultsController *frC = [[NSFetchedResultsController alloc]
initWithFetchRequest:fetchRequest
managedObjectContext:self.managedObjectContext
sectionNameKeyPath:nil
cacheName:@"Master"];
frC.delegate = self;
self.fetchedResultsController = frC;
NSError *error = nil;
if (![self.fetchedResultsController performFetch:&error]) {
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
return _fetchedResultsController;
}
专门无法弄清楚如何调用NSEntityDescription *entity
。 而解释的规格,我不能改写这个正确的..
迅速:
var fetchedResultsController: NSFetchedResultsController {
var _fetchedResultsController: NSFetchedResultsController? = nil //??
var fetchRequest: NSFetchRequest? = nil // ??
var entity: NSEntityDescription = NSEntityDescription(/*. . .*/) //??
fetchRequest.entity(entity) //?? sure this is wrong
...
return _fetchedResultsController
}
地狱啊。这工作。 –
我不明白,是不是应该用Swift删除实例变量?这两个变量是如何处理的?这方面最后一行的含义是什么? –
最后一行确实就像一个实例变量。奇怪的是,如果您查看AppDelegate.swift文件中的Core Data代码模板,则可以看到Apple在多个位置使用相同的技术,即_instanceVariable。 – iMaddin