swift - NSFetchedResultsController 部分按月

Question

我正在使用 NSFetchResultController 来显示表格中的部分。我有一个 NSDate 属性来按日期排序。我正在正确获取数据，我的问题是我希望这些部分显示一年中的月份，例如 七月、八月。目前日期显示如下图所示。

获取请求

var fetchResultController: NSFetchedResultsController = { () -> NSFetchedResultsController<Gratitude> in
    let fetchRequest = NSFetchRequest<Gratitude>(entityName: "Gratitude")
    let sortByDate = NSSortDescriptor(key: "date", ascending: false)
    fetchRequest.sortDescriptors = [sortByDate]
    let frc = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: Context.shared.persistentContainer.viewContext, sectionNameKeyPath: "date" , cacheName: nil)  
    return frc    
}()

标题

func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
    //return g2[section].monthLabel.uppercased()
   let sectionInfo = fetchResultController.sections?[section]
    return sectionInfo?.name
}

numberOfRowsInSection

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

    if let count = fetchResultController.sections?[section].numberOfObjects{
        return count
    }

    return 0
}

numberOfSections

func numberOfSections(in tableView: UITableView) -> Int {
    if let sections = fetchResultController.sections?.count {
        return sections
    }
   return 0

如有任何帮助，我们将不胜感激。

更新图片

Answer 1

好吧，那么我假设 sectionInfo?.name 为您提供了日期字符串，您必须将其转换为日期并从中获取月份。你可以这样做:

func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
  let sectionInfo = fetchResultController.sections?[section]
  return monthFrom(string: sectionInfo?.name)
}

//Make a function that converts any string with the format you showed above
//to the month for that string
func monthFrom(string: String?) -> String? {
  guard let dateString = string else { return nil }
  //Set up Date Formatter to create date object from the string
  let dateFormatter = DateFormatter()
  dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss +SSSS"
  //Verify string is a valid date
  guard let date = dateFormatter.date(from: dateString) else { return nil }
  //Pull month name from date
  dateFormatter.dateFormat = "MMMM"
  return dateFormatter.string(from: date)
}