Implement Unwrapped Cells for Improved Type Safety

[gokulvenkat243]

Issue: #1381

Description:

• Using Guard let statement they will be prevent the app crashes, when if the cells fails.

[whattherestimefor]

Thank you for noticing this. Please resubmit with the following change: rather than fatalError(), which will crash in production, return nil when the cell is nil or of an unexpected type:

guard let cell = dequeue...(...) as? OurTypeOfCell else {
    assertionFailure("unexpected cell type") // will crash in debug but not in production
    return nil
}

[whattherestimefor]

To avoid crashing in production, please use assertionFailure("unexpected cell dequeued") and then return nil.

[gokulvenkat243]

sure @whattherestimefor

[whattherestimefor]

Thank you for making these changes. A couple edits to the spots that aren't quite the same as the others and then this should be good to merge.

[whattherestimefor]

This block will never return nil (if _cell is nil, it will create a new PollOptionTableViewCell()), so the else will never be reached. Best fix would be to remove the ?? PollOptionTableViewCell(), so that the block can return nil and the new else can then be reached.

[whattherestimefor]

same as above

[whattherestimefor]

This is not a dequeued cell being provided to populate the tableview, but rather a cell that is already in the tableview and is being accessed to learn things about its contents. The assertion could be something like "unexpected cell type at (indexPath)"