如何在部分NSFetchedResultsController Swift中获取对象数量

Question

如何在Swift中的NSFetchedResultcController部分获取对象数？

    if let s = self.fetchedResultsController?.sections as? NSFetchedResultsSectionInfo {

    }

给我的Cannot downcast from '[AnyObject]' to non-@objc protocol type NSFetchedResultsSectionInfo

 var d = self.fetchedResultsController?.sections[section].numberOfObjects

给我does not have member named 'subscript'

Answer 1

你需要投self.fetchedResultsController?.sections到Array的NSFetchedResultsSectionInfo对象：

if let s = self.fetchedResultsController?.sections as? [NSFetchedResultsSectionInfo]

然后你可以将该section传递给下标并获得对象的数量：

if let s = self.fetchedResultsController?.sections as? [NSFetchedResultsSectionInfo] {
    d = s[section].numberOfObjects
}

Answer 2

我认为Mike S目前接受的答案是Swift 2.0

以下是为我工作（Swift 2.1）：

if let sections = fetchedResultsController?.sections {
    return sections[section].numberOfObjects
} else {
    return 0
}

Answer 3

这是我在UITableViewController （Swift 4）中的内容：

override func numberOfSections(in tableView: UITableView) -> Int {
    guard let sections = fetchedResultsController.sections else { return 0 }
    return sections.count
}