Question

我正在尝试将数据从第一个VC传递到我尝试使用委托的第二个VC，但它从未起作用（未显示所需的响应），所以我也尝试了回调，现在它也起作用了，所以我粘贴了两行代码，所以欢迎任何帮助

委托：

protocol RatingDelegate: class {
    func didLoadRating(ratings : [RatingModel])
}

要从中传递数据的viewcontroller

ViewController A：

var delegate : RatingDelegate?
func showRatings(ratings: [RatingModel]) {

        if delegate != nil {
            delegate?.didLoadRating(ratings: ratings)
        }
    }

应该在其中打印委托人值的地方

RatingVC：

extension RatingVC: RatingDelegate {
    func didLoadRating(ratings: [RatingModel]) {
        log(ratings)
    }

}

回调版本

将获取数据的视图控制器

var ratingsCallBack: (() -> ([RatingModel]))?

要从中传递值的视图控制器

func showRatings(ratings: [RatingModel]) {

        let ratingVC = RatingVC()
        ratingVC.ratingsCallBack!() = {[unowned self] in
            return ratings
        }
    }

这是怎么回事

表达式不可分配：函数调用返回不可变的值

Answer 1

因此FirstVC将数据传递给RatingVC。

在FirstVC上，当您调用RatingVC时，应该分配委托。

let ratingVC = RatingVC()
self.delegate = ratingVC //Here you specify RatingVC is the delegate variable

self.present(ratingVC, animated: true)

也

if delegate != nil {

}

是不必要的，只需执行delegate?.didLoadRating(ratings: ratings)使其保持清洁

编辑：对于回调版本相同，只需在初始化发送数据的视图控制器之前将值分配给回调即可。

Answer 2

看起来很奇怪：

var ratingsCallBack: (() -> ([RatingModel]))?

应该是这样的：

var ratingsCallBack: (([RatingModel]) -> ())?

以防回调：

class A: UIViewController {

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        let ratingVC = RatingVC()
        ratingVC.ratingsCallBack = { arr in
            arr.forEach({ (model) in
                print(model.rating)
            })
        }
        navigationController?.pushViewController(ratingVC, animated: false)
    }
}

class RatingVC: UIViewController {

    var ratingsCallBack: (([RatingModel]) -> ())?

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
    }

    @IBAction private func someButtonAction(_ sender: Any) {
        let arr = [RatingModel.init(rating: 5), RatingModel()]
        ratingsCallBack?(arr)
    }
}

struct RatingModel {
    var rating: Int = 1
}

然后，当您按“ someButton”时，将在控制器“ A”中获得此数组。

委托和回调不适用于传递模型数据

2 个答案: