Swift-代理用Weak修飾報錯問題

weak 屬性修飾會報錯。
‘weak’ must not be applied to non-class-bound ‘YJReaderRecommendOneBookViewProtocal’; consider adding a protocol conformance that has a class bound

weak與弱引用計數有關，只能修飾對象，不能修飾協議限制的any。

3個解決方案:

protocol YJReaderRecommendOneBookViewProtocal: NSObjectProtocol {
    func testProtocal1()
}

class TestVC: UIViewController {
    weak var delegate: YJReaderRecommendOneBookViewProtocal?
}

protocol YJReaderRecommendOneBookViewProtocal: class {
    func testProtocal1()
}

class TestVC: UIViewController {
    weak var delegate: YJReaderRecommendOneBookViewProtocal?
}

@objc protocol YJReaderRecommendOneBookViewProtocal {
    func testProtocal1()
}

class MyViewController: UIViewController {
    weak var delegate: YJReaderRecommendOneBookViewProtocal?
}