表达式的类型在Swift中不明确

Question

I have the following code using RxSwift :

 self.photos
                .bind(to: collectionView.rx.items(dataSource: self.dataSource))
                .disposed(by: disposeBag)

And it gives me Type of expression is ambiguous without more context

What more context does it need?

The complete code is shown below:

//
//  PhotosCollectionViewController.swift
//  TodoListRxSwift
//

//

import Foundation
import UIKit
import RxSwift
import RxCocoa
import RxDataSources

struct Photo  {
    var name :String
    var imageURL :String
}

struct SectionOfPhoto {
    var header: String
    var items: [Photo]
}
extension SectionOfPhoto: SectionModelType {

    init(original: SectionOfPhoto, items: [Photo]) {
        self = original
        self.items = items
    }
}

class PhotosCollectionViewController :UICollectionViewController {

    private let disposeBag = DisposeBag()

    private (set) var photos = BehaviorRelay(value: [Photo(name: "Pic 1", imageURL: "1.png"),Photo(name: "Pic 2", imageURL: "2.png"),Photo(name: "Pic 3", imageURL: "3.png")])

    let dataSource = RxCollectionViewSectionedReloadDataSource<SectionOfPhoto>(configureCell: { ds, cv, indexPath, photo in

        let cell = cv.dequeueReusableCell(withReuseIdentifier: "PhotoCollectionViewCell", for: indexPath)

        return cell

    })

    override func viewDidLoad() {

        super.viewDidLoad()

        self.collectionView?.delegate = nil
        self.collectionView?.dataSource = nil

        configureObservables()
    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

        prepareSegueForAddPhotoViewController(segue :segue)
    }

    override func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {

        switch kind {
            case UICollectionElementKindSectionHeader:

                let headerView = collectionView.dequeueReusableSupplementaryView(ofKind: UICollectionElementKindSectionHeader, withReuseIdentifier: "PhotosHeaderView", for: indexPath)
                return headerView

            default:
                return UICollectionReusableView()
        }

    }

    private func prepareSegueForAddPhotoViewController(segue :UIStoryboardSegue) {

        guard let nc = segue.destination as? UINavigationController else {
            fatalError("NavigationController does not exist")
        }

        guard let addPhotoVC = nc.topViewController as? AddPhotoViewController else {
            fatalError("AddPhotoViewController does not exist")
        }

        _ = addPhotoVC.selectedPhoto.subscribe(onNext: { (photo) in
           self.photos.accept(self.photos.value + [photo])
        })
    }


    private func configureObservables() {

        if let collectionView = self.collectionView {

            self.photos.bind(to: collectionView.rx.items(dataSource: self.dataSource))

            self.photos.bind(to: collectionView.rx.items(cellIdentifier: "PhotoCollectionViewCell", cellType: PhotoCollectionViewCell.self)) { row, model, cell in

                cell.photoImageView.image = UIImage(named: model.imageURL)

            }.disposed(by: disposeBag)

        }
    }
}

Answer 1

The problem is that photos is the wrong type. The data source is expecting an element of [SectionOfPhoto] , but photos has an element of [Photo] .

However, changing/fixing the type of photos will break addPhotoVC.selectedPhoto because it's trying to add a single photo to an array of sections.