ios – Swift：我的代表协议方法需要在另一个View Controller上执行

2019年8月4日 170次阅读

这是一个非常令人困惑的问题,所以我会尽力解释它.

我有视图控制器A,B,C,D和E.

我不确定我是否说得对,但重新说明一下,E需要与A交谈,但A和E之间没有设置委托的区别.

A> B> C> D> E>一个

有人告诉我,当你在swift中使用代理来访问视图控制器之间的数据时,你必须有很多东西：

>为对象B定义委托协议.
>为对象B提供可选的委托变量.这个变量应该很弱.
>当有趣的事情时,让对象B向其委托发送消息
发生,例如用户按下取消或完成按钮,或者当它
需要一条信息.
>使对象A符合委托协议.应该把它的名字
该类协议在其类行中实现协议中的方法.
>告诉对象B对象A现在是它的委托.

我一直在使用prepapreforsegue在视图控制器之间传递一个对象,因为它们从一个到另一个导航,在它们继续通过prepareforsegue方法时添加它.

在最终视图控制器上,我有协议方法,这些方法意味着要执行第一个视图控制器,但因为最后一个视图控制器从不同的视图控制器中分离.问题是它应该在第一个视图控制器上执行这些方法.如果没有第一个视图控制器能够告诉最后一个视图控制器它是segue,它怎么能达到它.

这是一些简单的代码,向您展示我的问题和我的意思.

第一：

import UIKit

class FirstViewController: UITableViewController, LastViewControllerDelegate {

var entry: EntryItem!

override func viewDidLoad() {
    super.viewDidLoad()
    entry = EntryItem()
    // Uncomment the following line to preserve selection between presentations
    // self.clearsSelectionOnViewWillAppear = false

    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem()
}

...

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

    //here's where I access the next view controller and set controller.entry and controller.delegate
    let controller = segue.destinationViewController as NextViewController
    controller.entry = entry
}

func lastViewControllerDidCancel(controller: LastViewController, didNotFinishAddingEntry draftentry: EntryItem){
    //this is where I wanna do something
    dismissViewControllerAnimated(true, completion: nil)
}
func lastViewController(controller: LastViewController, didFinishAddingEntry finalentry: EntryItem){
    //this is where I wanna do something
    dismissViewControllerAnimated(true, completion: nil)
}
}

下一个1：

import UIKit


class Next1ViewController: UITableViewController, LastViewControllerDelegate {

var entry: EntryItem!

override func viewDidLoad() {
    super.viewDidLoad()

    // Uncomment the following line to preserve selection between presentations
    // self.clearsSelectionOnViewWillAppear = false

    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem()
}

...

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    //here's where I access the next view controller and set controller.entry and controller.delegate
    let controller = segue.destinationViewController as Next2ViewController
    controller.entry = entry
}


}

下一个2：

import UIKit


class Next2ViewController: UITableViewController, LastViewControllerDelegate {

    var entry: EntryItem!

    override func viewDidLoad() {
        super.viewDidLoad()

        // Uncomment the following line to preserve selection between presentations
        // self.clearsSelectionOnViewWillAppear = false

        // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
        // self.navigationItem.rightBarButtonItem = self.editButtonItem()
    }

    ...

    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        //here's where I access the next view controller and set controller.entry and controller.delegate
        let controller = segue.destinationViewController as LastViewController
        controller.entry = entry
        controller.delegate = ???? //Not self, but needs to be the first one.
    }


}

持续：

import UIKit

protocol LastViewControllerDelegate: class {
    func lastViewControllerDidCancel(controller: LastViewController, didNotFinishAddingEntry draftentry: EntryItem)
    func lastViewController(controller: LastViewController, didFinishAddingEntry finalentry: EntryItem)
}

class LastViewController: UITableViewController {

weak var delegate: LastViewControllerDelegate?
var entry: EntryItem!

override func viewDidLoad() {
    super.viewDidLoad()

    // Uncomment the following line to preserve selection between presentations
    // self.clearsSelectionOnViewWillAppear = false

    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem()
}

...


@IBAction func cancel(){
    delegate?.lastViewControllerDidCancel(self, didNotFinishAddingEntry: entry)
}

@IBAction func done(){
    //do some final additions to entry object
    delegate?.lastViewController(self, didFinishAddingEntry: entry)
}

}

最佳答案 你不能让你的第一个视图控制器符合所有委托协议(或者,可能,制作一个委托协议,否则你会得到转换问题),然后不要这样做：

controller.delegate = self

做就是了

controller.delegate = self.delegate

或者,如果您已经删除了几个步骤,则使用通知通常比委派更好.如果介入视图控制器除了转发它之外没有委托的目的,您应该使用通知.

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