在 SwiftUI 中按 Date（） 对 CoreData 进行分组 列表为部分

您可以在sectionIdentifierentityextension@SectionedFetchRequest

return 变量只需要返回您的范围的共同点即可工作。

extension Todo{
    ///Return the string representation of the relative date for the supported range (year, month, and day)
    ///The ranges include today, tomorrow, overdue, within 7 days, and future
    @objc
    var dueDateRelative: String{
        var result = ""
        if self.dueDate != nil{
            //Order matters here so you can avoid overlapping
            if Calendar.current.isDateInToday(self.dueDate!){
                result = "today"//You can localize here if you support it
            }else if Calendar.current.isDateInTomorrow(self.dueDate!){
                result = "tomorrow"//You can localize here if you support it
            }else if Calendar.current.dateComponents([.day], from: Date(), to: self.dueDate!).day ?? 8 <= 0{
                result = "overdue"//You can localize here if you support it
            }else if Calendar.current.dateComponents([.day], from: Date(), to: self.dueDate!).day ?? 8 <= 7{
                result = "within 7 days"//You can localize here if you support it
            }else{
                result = "future"//You can localize here if you support it
            }
        }else{
            result =  "unknown"//You can localize here if you support it
        }
        return result
    }
}

然后用它来和你喜欢的@SectionedFetchRequest

@SectionedFetchRequest(entity: Todo.entity(), sectionIdentifier: \.dueDateRelative, sortDescriptors: [NSSortDescriptor(keyPath: \Todo.dueDate, ascending: true)], predicate: nil, animation: Animation.linear)
var sections: SectionedFetchResults<String, Todo>

也看看这个问题

您也可以使用，但必须选择一个日期作为部分标题。在此方案中，可以使用范围的 upperBound 日期，仅使用日期而不是时间，因为如果时间不匹配，则时间可能会创建其他部分。Date

extension Todo{
    ///Return the upperboud date of the available range (year, month, and day)
    ///The ranges include today, tomorrow, overdue, within 7 days, and future
    @objc
    var upperBoundDueDate: Date{
        //The return value has to be identical for the sections to match
        //So instead of returning the available date you return a date with only year, month and day
        //We will comprare the result to today's components
        let todayComp = Calendar.current.dateComponents([.year,.month,.day], from: Date())
        var today = Calendar.current.date(from: todayComp) ?? Date()
        if self.dueDate != nil{
            //Use the methods available in calendar to identify the ranges
            //Today
            if Calendar.current.isDateInToday(self.dueDate!){
                //The result variable is already setup to today
                //result = result
            }else if Calendar.current.isDateInTomorrow(self.dueDate!){
                //Add one day to today
                today = Calendar.current.date(byAdding: .day, value: 1, to: today)!
            }else if Calendar.current.dateComponents([.day], from: today, to: self.dueDate!).day ?? 8 <= 0{
                //Reduce one day to today to return yesterday
                today = Calendar.current.date(byAdding: .day, value: -1, to: today)!
            }else if Calendar.current.dateComponents([.day], from: today, to: self.dueDate!).day ?? 8 <= 7{
                //Return the date in 7 days
                today = Calendar.current.date(byAdding: .day, value: 7, to: today)!
            }else{
                today = Date.distantFuture
            }
        }else{
            //This is something that needs to be handled. What do you want as the default if the date is nil
            today = Date.distantPast
        }
        return today
    }
}

然后请求将如下所示......

@SectionedFetchRequest(entity: Todo.entity(), sectionIdentifier: \.upperBoundDueDate, sortDescriptors: [NSSortDescriptor(keyPath: \Todo.dueDate, ascending: true)], predicate: nil, animation: Animation.linear)
var sections: SectionedFetchResults<Date, Todo>

根据您提供的信息，您可以通过将我提供的扩展名粘贴到项目中的文件中，并将您的提取请求替换为您要使用的请求来测试此代码.swift

它抛出错误，因为这是你告诉它要做的。 将部分标识符和实体类型的元组发送到 ，因此您指定的元组必须匹配。就你而言，你写道：@SectionedFetchRequestSectionedFetchResultsSectionedFetchResults

SectionedFetchResults<String, Todo>

但是你要做的是传递一个日期，所以它应该是：

SectionedFetchResults<Date, Todo>

Lorem ipsum 击败了我，在扩展中使用计算变量来提供部分标识符的第二个，也是更重要的部分。根据他的回答，你应该回到：

SectionedFetchResults<String, Todo>

请接受 lorem ipsum 的回答，但要意识到您也需要处理这个问题。

按“今天”、“明天”、“未来 7 天”等进行分段。

我的建议是使用 Apple 并让 Apple 完成大部分或全部工作。要创建一个计算变量来分割，你需要创建一个扩展，如下所示：RelativeDateTimeFormatterTodo

extension Todo {
    
    @objc
    public var sections: String {
        // I used the base Xcode core data app which has timestamp as an optional.
        // You can remove the unwrapping if your dates are not optional.
        if let timestamp = timestamp {
            // This sets up the RelativeDateTimeFormatter
            let rdf = RelativeDateTimeFormatter()
            // This gives the verbose response that you are looking for.
            rdf.unitsStyle = .spellOut
            // This gives the relative time in names like today".
            rdf.dateTimeStyle = .named

            // If you are happy with Apple's choices. uncomment the line below
            // and remove everything else.
  //        return rdf.localizedString(for: timestamp, relativeTo: Date())
            
            // You could also intercept Apple's labels for you own
            switch rdf.localizedString(for: timestamp, relativeTo: Date()) {
            case "now":
                return "today"
            case "in two days", "in three days", "in four days", "in five days", "in six days", "in seven days":
                return "this week"
            default:
                return rdf.localizedString(for: timestamp, relativeTo: Date())
            }
        }
        // This is only necessary with an optional date.
        return "undated"
    }
}

您必须将变量标记为 ，否则 Core Data 将导致崩溃。我认为 Core Data 将是 Obj C 的最后一个地方，但我们可以很容易地像这样将 Swift 代码与它连接起来。@objc

回到您的视图中，您的外观如下所示：@SectionedFetchRequest

@SectionedFetchRequest(
    sectionIdentifier: \.sections,
    sortDescriptors: [NSSortDescriptor(keyPath: \Todo.timestamp, ascending: true)],
    animation: .default)
private var todos: SectionedFetchResults<String, Todo>

然后，您的列表如下所示：

 List {
      ForEach(todos) { section in
          Section(header: Text(section.id.capitalized)) {
               ForEach(section) { todo in
               ...
               }
          }
      }
  }

您可以使用此方法来实现： 喜欢这个：

func formattedDate () -> String? {
    let RFC3339DateFormatter = DateFormatter()
    RFC3339DateFormatter.locale = Locale(identifier: "en_US_POSIX")
    RFC3339DateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZZZZZ"
    RFC3339DateFormatter.timeZone = TimeZone(secondsFromGMT: 0)
    let date1 = RFC3339DateFormatter.date(from: date.formatted()) ?? Date()
    
    let dateFormatter = DateFormatter()
    dateFormatter.dateStyle = .medium
    dateFormatter.timeStyle = .none
     
    // ES Spanish Locale (es_ES)
    dateFormatter.locale = Locale.current//Locale(identifier: "es_ES")
    return dateFormatter.string(from: date1) // Jan 2, 2001
}