我想在IB中连接一个自定义的swift委托。委托是一个在swift中实现某个协议的对象。

I would like to wire up a custom swift delegate in IB. The delegate is an object that implements a certain protocol in swift.

protocol ThumbnailTableViewCellDelegate {
    func cellWasTouched(thumbnail: Bool, cell: UITableViewCell)
}

class ThumbnailTableViewCell: UITableViewCell {
    @IBOutlet var thumbnailTableViewCellDelegate: ThumbnailTableViewCellDelegate?
}

不幸的是，编译器抱怨：

unfortunately, the compiler complains with:

error: 'IBOutlet' property cannot have non-object type 'ThumbnailTableViewCellDelegate'
    @IBOutlet var thumbnailTableViewCellDelegate: ThumbnailTableViewCellDelegate?
    ^~~~~~~~~