constraints_generic.swift

protocol ReusableViewType: class {
    static var defaultReuseIdentifier: String { get }
    static var nib: UINib { get }
}

extension ReusableViewType where Self: UIView {
    
    static var defaultReuseIdentifier: String {
        return NSStringFromClass(self)
    }
    
    static var nib: UINib {
        let bundle = Bundle(for: Self.self)
        let nibName = NSStringFromClass(self).components(separatedBy: ".").last!
        let nib = UINib(nibName: nibName, bundle: bundle)
        
        return nib
    }
    
}

extension UITableView {
    
    func register<T: UITableViewCell>(_: T.Type) where T: ReusableViewType {
        register(T.nib, forCellReuseIdentifier: T.defaultReuseIdentifier)
    }
    
}

class Cell: UITableViewCell, ReusableViewType {}

let tableView = UITableView()
// Regular Cell registration
tableView.register(UINib(nibName: "Nib", bundle: Bundle.main), forCellReuseIdentifier: "CellIdentifier")

// Constrainted generic extension in Action
tableView.register(Cell.self)