按日期()将SWIFTUI列表中的CoreData分组为节 [英] Grouping CoreData by Date() in SwiftUI List as sections

问题描述

我的目标：

我希望能够按CoreData待办事项的过期范围对其进行分组。(今天&q；、明天&q；、未来7天&q；)

我尝试的内容.

我尝试使用@SectionedFetchRequest，但sectionIdentifier需要字符串。如果它作为日期()存储在CoreData中，我如何转换它以供使用呢？我收到了许多错误和建议，但都无济于事。这也不适用于日期范围，如&Quot；NEXT 7 DATE&QOOT；。此外，我似乎甚至没有访问实体的duedate，因为它指向我的ViewModel表单。

    @Environment(.managedObjectContext) private var viewContext
    
    //Old way of fetching Todos without the section fetch
    //@FetchRequest(sortDescriptors: []) var todos: FetchedResults<Todo>
    
    @SectionedFetchRequest<String, Todo>(
        entity: Todo.entity(), sectionIdentifier: Todo.dueDate,
        SortDescriptors: [SortDescriptor(.Todo.dueDate, order: .forward)]
    ) var todos: SectionedFetchResults<String, Todo>

Cannot convert value of type 'KeyPath<Todo, Date?>' to expected argument type 'KeyPath<Todo, String>'

Value of type 'NSObject' has no member 'Todo'

询问

有没有比@SectionedFetchRequest?更适合我的情况的解决方案。如果没有，我希望看到如何对数据进行适当分组。

推荐答案

您可以在entityextension中制作您自己的sectionIdentifier，@SectionedFetchRequest

返回变量只需返回您的范围共有的内容，它才能正常工作。

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
    }
}

然后将其与您的@SectionedFetchRequest一起使用，如下所示

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

也查看this question

您也可以使用Date，但您必须选择一个日期作为节标题。在此方案中，您可以使用范围的上行日期，只使用日期而不是时间，因为如果它们不匹配，时间可能会创建其他部分。

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，您可以测试此代码，方法是将我提供的扩展粘贴到项目的.swift文件中，并将获取请求替换为您要使用的请求

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