相关疑难解决方法(0)

我试图在所有符合协议的UIViewControllers中添加点按功能MyProtocol。

以下是我的做法：

import UIKit

protocol MyProtocol: class{
    var foo: String? {get set}
    func bar()
}


extension MyProtocol where Self: UIViewController {
    func bar() {
        print(foo)
    }
}


class TestViewController: UIViewController, MyProtocol{
    var foo: String?

    override func viewDidLoad() {
        super.viewDidLoad()

        foo = "testing"
        let tapGesture = UITapGestureRecognizer(target: self, action: "bar")
}

点击屏幕时，结果如下：

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: unrecognized selector sent to instance

我了解该错误，但不知道如何解决。谁能建议如何做到这一点？