ios - 协议(protocol)和委托(delegate)不起作用..我做错了什么？

Question

我正在尝试通过委托(delegate)和协议(protocol)将图像从我的collectionViewCell imageView发送到另一个VC中的imageView。我不明白为什么这不能正常工作？

发送 VC 是:TrainersViewController接收 VC 是:BioViewController

这是我的协议(protocol):

protocol TrainersViewControllerDelegate: class {

    func trainersViewController(controller: TrainersViewController, didFinishSendingImage trainer:TrainerArray)
}


class TrainersViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate, AddNewTrainerViewControllerDelegate {

    weak var delegate: TrainersViewControllerDelegate? 
}

这是我的接收类:

class BioViewController: UIViewController, TrainersViewControllerDelegate {


    @IBAction func backToTrainersButton(sender: AnyObject) {

        dismissViewControllerAnimated(true, completion: nil)
    }

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    @IBOutlet weak var bioImage: UIImageView!


    func trainersViewController(controller: TrainersViewController, didFinishSendingImage trainer: TrainerArray) {

        trainer.trainerImage! = bioImage as! UIImage
    }

    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {

        if segue.identifier == "bioSegue" {
            let navigationController = segue.destinationViewController as! UINavigationController
            let controller = navigationController.topViewController as! TrainersViewController
            controller.delegate = self
        }
    }
}

最后，这是我调用来实现此目的的 collectionViewCell 中的按钮:

    @IBAction func bioSegueButton(sender: AnyObject) {
    let index = sender.tag
    let trainer = trainers[index]
    print(trainer.name)
    delegate?.trainersViewController(self, didFinishSendingImage: trainer)
    performSegueWithIdentifier("bioSegue", sender: self)
}

为什么这没有将我的图像发送到另一个 VC 的 imageView 中？

Answer 1

当你打电话的时候

delegate?.trainersViewController(self, didFinishSendingImage: trainer)

变量delegate尚未设置。您可以使用以下行进行检查:

print(delegate)

如果未设置委托(delegate)，则此行将打印 nil