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Project 9 in Hacking with iOS: UIKit Edition

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On page 343, there are two calls to performSelector(onMainThread:with:waitUntilDone:). The first one appears as tableView.performSelector, but the second is simply performSelector. Why do these differ from each other? Is it because the first one is calling UITableView.reloadData?

I ask because Xcode 12.4 complains about the first call ("UITableViewController.tableView must be used from main thread only"). It seems to work in spite of this complaint, but I suspect something has changed in Swift since the book was written, so this code may not be strictly correct any more. If I change tableView.performSelector to a bare performSelector, the code crashes. How can we make the call to assign the reloadData operation to the main thread without a reference to tableView (or is that the wrong idea)?

Thanks!

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