Swift Error: nib must contain exactly one top level object which must be a UITableViewCell instance

I'm developing a pet project, which requires loading a UITableViewCell from a XIB file. At first, it worked fine but after making some changes, I got the error when the system trying to load the UITableViewCell from a nib file to construct the UITableView object.

Cause

It's because I accidentally dragged a Tap Gesture Recognizer from the Object Library and dropped it on the UITableViewCell in IB.

Solution

Click on the Tap Gesture Recognizer icon and press Delete key.