符合协议/分页

Question

我试图将我的主页图片分页，以便不会一次性加载我的所有元素。我有一个活动模型

import Foundation
import FirebaseDatabase.FIRDataSnapshot


    struct  Event: MGKeyed {
    let currentEventKey: String
    let currentEventName: String
    let currentEventImage: String
    let currentEventPromo: String?
    let currentEventDescription: String
    //nested properties
    let currentEventStreetAddress: String
    let currentEventCity: String
    let currentEventState: String
    let currentEventDate: String?
    let currentEventTime: String?
    let currentEventZip: Int
    //nested properties stop
    var currentAttendCount: Int
    var isAttending = false

    var eventDictionary: [String: Any]{


        let dateDict = ["start:date":currentEventDate, "start:time": currentEventTime]

        return ["event:name":currentEventName,"event:imageURL" : currentEventImage,
                "event:description": currentEventDescription, "attend:count": currentAttendCount,
                "event:street:address": currentEventStreetAddress,"event:zip": currentEventZip,
                "event:state": currentEventState, "event:city": currentEventCity, "event:promo": currentEventPromo ?? "", "event:date": dateDict]
    }

    init(currentEventKey: String, dictionary: [String:Any]) {
        self.currentEventKey = currentEventKey
        self.currentEventName = dictionary["event:name"] as? String ?? ""
        self.currentEventImage = dictionary["event:imageURL"] as? String ?? ""
        self.currentEventDescription = dictionary["event:description"] as? String ?? ""
        self.currentEventPromo = dictionary["event:promo"] as? String ?? ""
        self.currentAttendCount = dictionary["attend:count"] as? Int ?? 0
        //nested properties
        self.currentEventStreetAddress = dictionary["event:street:address"] as? String ?? ""
        self.currentEventCity = dictionary["event:city"] as? String ?? ""
        self.currentEventState = dictionary["event:state"] as? String ?? ""
        self.currentEventZip = dictionary["event:zip"] as? Int ?? 0
        let eventDate = dictionary["event:date"] as? [String: Any]
        self.currentEventDate = eventDate?["start:date"] as? String ?? ""
        self.currentEventTime = eventDate?["start:time"] as? String ?? ""
    }

    init?(snapshot: DataSnapshot) {
        guard let dict = snapshot.value as? [String : Any],
            let currentEventName = dict["event:name"] as? String,
            let currentEventImage = dict["event:imageURL"] as? String,
            let currentEventDescription = dict["event:description"] as? String,
            let currentEventPromo = dict["event:promo"] as? String,
            let currentEventStreetAddress = dict["event:street:address"] as? String,
            let currentEventCity = dict["event:city"] as? String,
            let currentEventState = dict["event:state"] as? String,
            let currentEventZip = dict["event:zip"] as? Int,
            let currentAttendCount = dict["attend:count"] as? Int,
            let eventDate = dict["event:date"] as? [String: Any],
            let currentEventDate = eventDate["start:date"] as? String,
            let currentEventTime = eventDate["start:time"] as? String
            else { return nil }
        self.currentEventKey = snapshot.key
        self.currentEventName = currentEventName
        self.currentEventImage = currentEventImage
        self.currentEventDescription = currentEventDescription
        self.currentEventStreetAddress = currentEventStreetAddress
        self.currentEventCity = currentEventCity
        self.currentEventState = currentEventState
        self.currentEventZip = currentEventZip
        self.currentAttendCount = currentAttendCount
        self.currentEventPromo = currentEventPromo
        self.currentEventDate = currentEventDate
        self.currentEventTime = currentEventTime
    }




    }

此事件要求我遵守下面列出的MGKeyed协议

     import Foundation
     import UIKit
     protocol MGKeyed {
    var key: String? { get set }
     }

     class MGPaginationHelper <T: MGKeyed> {

    let pageSize: UInt
    let serviceMethod: (UInt, String?, @escaping (([T]) -> Void)) -> Void
    var state: MGPaginationState = .initial
    var lastObjectKey: String?

    init(pageSize: UInt = 1, serviceMethod: @escaping (UInt, String?, @escaping (([T]) -> Void)) -> Void) {
        self.pageSize = pageSize
        self.serviceMethod = serviceMethod
    }

    // 1
    func paginate(completion: @escaping ([T]) -> Void) {
        // 2
        switch state {
        // 3
        case .initial:
            lastObjectKey = nil
            fallthrough

        // 4
        case .ready:
            state = .loading
            serviceMethod(pageSize, lastObjectKey) { [unowned self] (objects: [T]) in
                // 5
                defer {
                    // 6
                    if let lastObjectKey = objects.last?.key{
                        self.lastObjectKey = lastObjectKey
                    }

                    // 7
                    self.state = objects.count < Int(self.pageSize) ? .end : .ready
                }

                // 8
                guard let _ = self.lastObjectKey else {
                    return completion(objects)
                }

                // 9
                let newObjects = Array(objects.dropFirst())
                completion(newObjects)
            }

        // 10
        case .loading, .end:
            return
        }
    }

    func reloadData(completion: @escaping ([T]) -> Void) {
        state = .initial

        paginate(completion: completion)
    }
    }

    enum MGPaginationState {
    case initial
    case ready
    case loading
    case end
    }

此方法负责分页。我的第一个问题是分页永远不会停止并继续加载相同的1或2个元素，我假设这是因为协议的符合性。我如何使我的事件模型符合该协议，因此它获得了一个不同的密钥，因此它知道何时停止？