UICollectionViewCell gets draggable when elements are binded via rx.items(dataSource:)

[ishkawa]

Short description of the issue:

UICollectionViewCell gets draggable when elements are binded via rx.items(dataSource:), even if the delegate does not have implementation of collectionView(_:canMoveItemAtIndexPath:).

Expected outcome:

UICollectionViewCell is not draggable by default.

What actually happens:

UICollectionViewCell is draggable by default.

Self contained code example that reproduces the issue:

import UIKit
import RxSwift
import RxCocoa

class Cell: UICollectionViewCell {
    @IBOutlet weak var label: UILabel!
}

class ViewController: UICollectionViewController {
    private let dataSource = DataSource()
    private let disposeBag = DisposeBag()
    
    override func viewDidLoad() {
        super.viewDidLoad()

        let values = Array(1...100)

        Observable
            .just(values)
            .bindTo(collectionView!.rx.items(dataSource: dataSource))
            .addDisposableTo(disposeBag)
    }

    class DataSource: NSObject, UICollectionViewDataSource, RxCollectionViewDataSourceType {
        typealias Element = [Int]

        var values = [Int]()

        func collectionView(_ collectionView: UICollectionView, observedEvent: Event<Element>) {
            if case .next(let element) = observedEvent {
                values = element
                collectionView.reloadData()
            }
        }

        func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
            return values.count
        }

        func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
            let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! Cell
            cell.label.text = String(indexPath.row)

            return cell
        }
    }
}

Entire project is available here. Run carthage bootstrap and open RxCocoaReorderIssue/Demo.xcodeproj to reproduce the issue.

RxSwift/RxCocoa/RxBlocking/RxTest version/commit

3.1.0

Platform/Environment

• iOS
• macOS
• tvOS
• watchOS
• playgrounds

How easy is to reproduce? (chances of successful reproduce after running the self contained code)

• easy, 100% repro
• sometimes, 10%-100%
• hard, 2% - 10%
• extremely hard, %0 - 2%

Xcode version:

8.2.1

Installation method:

• CocoaPods
• Carthage
• Git submodules

I have multiple versions of Xcode installed:
(so we can know if this is a potential cause of your issue)

• yes (8.2.1 and 7.3.1)
• no

Level of RxSwift knowledge:
(this is so we can understand your level of knowledge
and formulate the response in an appropriate manner)

• just starting
• I have a small code base
• I have a significant code base

[kzaher]

Hi @ishkawa,

I think you can temporarily use self.installsStandardGestureForInteractiveMovement = false to solve this issue.

Long term solution would require modifying RxCollectionViewDataSourceProxy to use something like

#907
c005b1a

It would probably make sense to make CachedCommitForRowAt more generic.

Do you maybe have time to help out with this?

[ishkawa]

Yes, I'll try to fix this issue.

[kzaher]

HI @ishkawa ,

I think #1087 is related to this issue also. It looks like it might be worth solving this in delegate proxy layer.