在非转义函数中处理转义闭包

Question

在下面的代码中我得到了错误。

Passing non escaping parameter 'completion' to function expecting an @escaping closure.

protocol DetailViewControllerDelegate: AnyObject {
    func detailViewController(_ controller: DetailViewController, doneButtonPressed button: UIBarButtonItem)
}

final class DetailViewControllerDelegateHandler: DetailViewControllerDelegate {
    
    typealias DismissComplete = () -> Void
    typealias Action = (DismissComplete) -> Void
    
    var dissmissScene: Action?
    
    private let model = Model()

    func detailViewController(_ controller: DetailViewController, doneButtonPressed button: UIBarButtonItem) {
        
        dissmissScene? { [unowned self] in
            let value = controller.value
            self.model.update(with: value)
        }
    }
}

final class HomeViewController: UIViewController {

    private let delegateHandler = DetailViewControllerDelegateHandler()

    override func viewDidLoad() {
        super.viewDidLoad()

        delegateHandler.dissmissScene = { completion in
            // error here
            self.dismiss(animated: true, completion: completion)
        }
    }

    func buttonAction(_ sender: UIButton) {
        let controller = DetailViewController.instantiateFromStoryboard()
        controller.delegate = delegateHandler
        present(controller, sender: self)
    }
}

我该怎么办？

Answer 1

completion 闭包没有转义。因为 dismissScene 是一个接受 non-escaping 闭包的函数。请注意，dismissScene 的类型是 Action，即 (DismissComplete) -> Void，而后者又是 (() -> Void) -> Void。里面的() -> Void没有标注@escaping.

您只需将其标记为：

typealias Action = (@escaping DismissComplete) -> Void

在非转义函数中处理转义闭包

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