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

Question

如何在Swift中获取NSFetchedResultcController部分中的对象数？

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

    }

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

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

给了我does not have member named 'subscript'

Answer 1

您需要将self.fetchedResultsController?.sections投射到Array个NSFetchedResultsSectionInfo个对象：

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

然后你可以将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之前的

以下内容对我有用（Swift 2.1）：

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

Answer 3

这就是我的UITableViewController中的内容（快速4）：

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