来自故事板的 UIViewController 的自定义初始化 [英] Custom init of UIViewController from storyboard

问题描述

我试着找了一些相关的问题，但没有得到任何东西，希望有人能帮忙.

I tried finding some relevant questions but couldn't get anything, hope someone can help.

我在情节提要上设置了一些 UIViewController.然后我想在代码中加载一个视图控制器并将其推送到导航堆栈上.我想出正确的方法是使用

I set up some UIViewController's on a storyboard. I then want to load one of the view controllers in code and push it onto the navigation stack. I figure out the right way to do this is to use

instantiateViewControllerWithIdentifier

这会调用 init(coder: NSCoder) 并且一切正常，我的程序可以运行，但是我希望能够有一个自定义初始值设定项，为我的视图控制器设置一些变量.考虑以下几点:

This calls init(coder: NSCoder) and all is well, my program works, but I want to be able to have a custom initializer that sets up some variables for my view controller. Consider the following:

class A : UIViewController {   

  let i : Int

  required init(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
    // property self.i not initialized at super.init call   
  }

}

我显然得到一个错误，因为 i 需要在创建对象时指定.有什么解决办法吗?我对将 i 声明为 var 并稍后配置它不感兴趣，因为这违背了这一点，而且我不再有编译器保证 i 是不可变.

I obviously get an error since i needs to be specified at time of object creation. Any solutions to this? I am not interested in declaring i as var and configuring it later as that defeats the point and I no longer have a compiler guarantee that i is immutable.

假设我有一个当前加载的 ViewController，它有一些变量 i.这个值是可变的并且可以改变.现在假设我想从这个 ViewController 展示另一个，并用 i 初始化它.

Suppose I have a currently loaded ViewController that has some variable i. This value is variable and can change. Now suppose from this ViewController I want to present another one, and initialize it with i.

class ViewController: UIViewController {

   var i : Int

   // ... other things

  // in response to some button tap...
  @IBAction func tappedButton(sender: AnyObject) {
    let st = UIStoryboard(name: "Main", bundle: nil)
    let vc = st.instantiateViewControllerWithIdentifier("AControllerID") as! A
    // How do I initialize A with i ?
    self.presentViewController(vc, animated: true, completion: nil)
  }

}

我似乎无法做到这一点并通过使用 let 而不是 var 来保持 i 不可变.

I don't seem to be able to do this and keep i immutable by using let instead of var.

推荐答案

我之前的答案的简化，它是快速的并且避免了替代的 hacky 修复:

A simplification of my prior answer which is quick and avoids alternative hacky fixes:

这里是一个细节视图控制器，你可能想用一个 objectID 集从故事板实例化:

Here is a detail view controller you may want to instantiate from storyboard with an objectID set:

import UIKit

class DetailViewController: UIViewController {

    var objectID : Int!

    internal static func instantiate(with objectID: Int) -> DetailViewController {

        let vc = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "DetailViewController") as DetailViewController
        vc.objectID = objectID
        return vc
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        if((objectID) != nil){
            print("Here is my objectID: (objectID)")
        }
    }
}

以下是您将如何使用它来推送对象 ID 设置为 1 的导航控制器:

Here is how you would use it to push onto a navigation controller with objectID set to 1:

self.navigationController.pushViewController(DetailViewController.instantiate(1), animated: true)

添加了一篇博文:https://theswiftcook.wordpress.com/2017/02/17/how-to-initialize-a-storyboard-viewcontroller-with-data-without-segues-swift-3-0git/

链接到 GitHub 上的示例:https://github.com/hammadzz/Instantiate-ViewController-From-Storyboard-With-Data

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