UITableView shows delete button on swipe cell by default

[ishkawa]

Short description of the issue:

UITableView which displays cells using rx.items has unwanted editingStyle. It should have .none by default, but it seems to be set as .delete. Here's a screen shot of the bug that appeared in RxExample.

Self contained code example that reproduces the issue:

https://github.com/ReactiveX/RxSwift/blob/e4e422c4f1da21aa78d9a4c982c572533f74645d/RxExample/RxExample/Examples/SimpleTableViewExample/SimpleTableViewExampleViewController.swift

Xcode version:

Version 8.0 (8A218a)

Expected outcome:

UITableView doesn't show delete button by default.

What actually happens:

UITableView shows delete button by default.

[kzaher]

Hi @ishkawa ,

That's actually part of Apple black magic :)

If your delegate implements

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath;

and Rx delegate "does" because it fits under observable event spectrum, then UIKit has that unfortunate behavior.

You can test it out by temporarily modifying this code in _RxDelegateProxy.m

-(BOOL)respondsToSelector:(SEL)aSelector {
    if (aSelector == @selector(tableView:commitEditingStyle:forRowAtIndexPath:)) {
        return NO;
    }
    return [super respondsToSelector:aSelector]
    || [self._forwardToDelegate respondsToSelector:aSelector]
    || [self canRespondToSelector:aSelector];
}

The solution for this is simple, but annoying.

    // viewDidLoad
    tableView.rx
            .setDelegate(self)
            .addDisposableTo(disposeBag)

// to prevent swipe to delete behavior
func tableView(_ tableView: UITableView, editingStyleForRowAt indexPath: IndexPath) -> UITableViewCellEditingStyle {
    return .none
}

[ishkawa]

I understood what is happening. I didn't notice the cause of this issues is tableView(_:commit:forRowAt:), because I didn't know the method has such side-effect.

Thank you for the concise explanation 👍

BTW, my project contains approximately 20 tableView(_:editingStyleForRowAt:) to workaround this issue, but I don't think all users of RxCocoa have to do that.

Instead of implementing the delegate method in each view controllers, I suggest overriding responds(to:) of RxTableViewDataSourceProxy to avoid forwarding invocation of tableView(_:editingStyleForRowAt:) until itemInserted or itemDeleted is subscribed.

[ishkawa]

If the policy I suggested is OK, I will work on it.
Here's rough implementation: ishkawa@a086f9c

[kzaher]

Hi @ishkawa ,

Apple's black magic is stong :)

UITableView and UICollectionView cache a list of possible selectors once delegate or dataSource is set, so one would need to set delegate or dataSource once number of observers is changed. There are also some threading concerns, etc ...

I would like to take some time and think what is the simplest way to solve this, there is a lot of possible solutions out there, including some similar to one you've suggested.

[ishkawa]

UITableView and UICollectionView cache a list of possible selectors once delegate or dataSource is set, so one would need to set delegate or dataSource once number of observers is changed. There are also some threading concerns, etc ...

😇

I would like to take some time

I agree with you. It needs further consideration.

[kzaher]

I think this should be solved now.

@ishkawa please let me know if this doesn't work. I'll close issue for now.