如何查询我的数据并将其按类别存储在数组中，以便在TableView中按类别显示它们？

Question

I wish to display my events by category in my TableView where each TableViewCell is a category, with its events found in a CollectionView embedded within the TableViewCell.

Here is a sample initialised prototype of what I want to achieve.

    var events = [Events]()
    var eventCategory = [EventCategory]()

    var testEvent1 = Events(id: 1, event_name: "PrototypeEvent", event_category: "Party", event_date: "10/06/19", event_img_url: "null")
    var testEvent2 = Events(id: 2, event_name: "PrototypeEvent2", event_category: "Music", event_date: "11/06/19", event_img_url: "null")

    override func viewDidLoad() {
        super.viewDidLoad()

        var eventArray = [testEvent1]
        var eventArray1 = [testEvent2]

        var category1 = EventCategory(title: "Party", events: eventArray)
        var category2 = EventCategory(title: "Music", events: eventArray1)
        eventCategory.append(category1)
        eventCategory.append(category2)
    }

    func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return eventCategory.count
    }

    func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
        return 245
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "PopularCell", for: indexPath) as! PopularCell
        let category = eventCategory[indexPath.row]
        for event in category.events! {
            print("Event Name:\(event.event_name)")
        }
        cell.eventCategory = category

        return cell
    }

Answer 1

make an enum for event_category:

enum EventCategory {
    case music
    case party
    ...
}

then use the grouping init of Dictionary

let eventsDictionary = Dictionary(grouping: events) { (element) -> EventCategory in
        return element.event_category
}

you will have a dictionary like this [EventCategory: [Events]] ; it's will be an easy use for tableView indexPath.row to show a category for every row

Answer 2

You can group the Events based on category using Dictionary's init, ie

init(grouping:by:)

Creates a new dictionary whose keys are the groupings returned by the given closure and whose values are arrays of the elements that returned each key.

var groupedEventsDict = Dictionary(grouping: events) { $0.event_category }

groupedEventsDict will be of type [String:[Events]] , where key is the event_category and value is the array of Events lying under that event_category .

Now, since you need an array for UITableViewDataSource , you need to create an array from groupedEventsDict .

var groupedEventsArr = Dictionary(grouping: events) { $0.event_category }.compactMap({( $0.key, $0.value )})

So, your dataSource methods look something like:

func numberOfSections(in tableView: UITableView) -> Int {
    return 1
}

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return groupedEventsArr.count
}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "PopularCell", for: indexPath)
    let (category, events) = self.groupedEventsArr[indexPath.row]
    print("Category: \(category)")
    events.forEach {
        print("Event Name:\($0.event_name)")
    }
    return cell
}