通过字典中的日期对表格视图进行剖分 [英] Sectioning a tableview by dates from a dictionary

问题描述

我有一个字典，其中包含Date的键/值对，Date包含按相同日期分组在一起的我的自定义对象Meals的数组.

I have a dictionary that contains a key/value pair of a Date that contains an array of my custom object Meals grouped together by the same dates.

膳食对象:

class Meal: NSObject, Codable {

var id: String?
var foodname: String?
var quantity: Float!
var brandName: String?
var quantityType: String?
var calories: Float!
var date: Date?
}

在我的TableView中:

In my TableView:

var grouped = Dictionary<Date, [Meal]>()
var listOfAllMeals = [Meal]() //already populated

self.grouped = Dictionary(grouping: self.listOfAllMeals.sorted(by: { ($0.date ?? nilDate) < ($1.date ?? nilDate) }),
            by: { calendar.startOfDay(for: $0.date ?? nilDate) })

override func numberOfSections(in tableView: UITableView) -> Int {
    // #warning Incomplete implementation, return the number of sections
    return grouped.count
}

override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
    return Array(grouped.keys)[section] as! String //this throws a thread error
}

这允许用户每天多次上载餐点以供将来查看，现在我想在TableView中显示餐点，按日期将其分段，并按最新的日期进行排序.我该如何实现?

This allows users to upload a meal multiple times a day for future viewing and now I want to show the meals in a TableView sectioned by their dates and sorted already by the latest. How do I achieve that?

推荐答案

为各节创建结构

struct Section {
    let date : Date
    let meals : [Meal]
}

并将分组字典映射到Section

var sections = [Section]()

let sortedDates = self.grouped.keys.sorted(>)
sections = sortedDates.map{Section(date: $0, meals: self.grouped[$0]!)}

您可以添加日期格式化程序以显示Date实例更有意义.

You could add a date formatter to display the Date instance more meaningful.

表视图数据源方法是

override func numberOfSections(in tableView: UITableView) -> Int {
    return sections.count
}

override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {        
    return sections[section].date.description
}

override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return sections[section].meals.count
}

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "foodCell", for: indexPath)
    let meal = sections[indexPath.section].meals[indexPath.row]
    ...

注意:

考虑使用较少的可选内容和结构，而不要使用NSObject子类.与NSCoding不同，Codable不需要符合NSObjectProtocol.并且从不将属性声明为隐式未包装的可选.

Consider to use less optionals and a struct rather than a NSObject subclass. Unlike NSCoding Codable does not require to conform to NSObjectProtocol. And never declare properties as implicit unwrapped optional.

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