以静态方式返回UIViewController中的子类 [英] Returning the subclass in a UIViewController static

问题描述

  class客房：UIViewController {
 class func instantiate（） - >房间{
} 
 
 static func make（） - >房间{
 let emplacedAndSetup = self.instantiate（）
 //各种kodes here 
 //很可能把s.view放在某处
 return emplacedAndSetup 
} 
 
 sundryOtherFunctionality（）
} 
  

（请注意 instantiate（）之前的 self。看起来有必要获得那个实例化器。）

每个子类都知道它自己的故事板ID以便如何使用 instantiateViewController < code $：



  class Dining：客房{
覆盖类func实例化（） - >餐饮{ //返回一个Dining
让d = stbd.instantiateViewController（
 withIdentifier：Some Specific Sc​​ene）as！餐厅
返回d 
} 
} 
班Bath：客房{
覆盖class func instantiate（） - > Bath {//返回一个Bath
让b = stbd.instantiateViewController（
 withIdentifier：Some Other Scene）as！ Bath 
 return b 
} 
} 
  

您可以做到这一点，



  let d = Dining.make（）
 let r = Bath.make（）
  

唯一的小问题是，它返回基类。 但看下面。 因此，实际上你必须



  let d = Dining.make（）as！用餐
让r = Bath.make（）as！ Bath 
  

有没有办法修改静态 make 确实 Dining.make（）会返回一个 Dining 和 Bath.make （）会返回一个巴斯？

（@Hamish指出，可以使用 init 和 Self 模式，返回被调用的类型对象的方法但是，我认为这是不可能的，因为 instantiateViewController 。）

---

所以。假设你有如下代码：
$ b

  let d = Dining.make（blah blah）
 实际上，

运行时，d确实变成了餐饮，而不是房间 这非常棒。

但是。如果您在IDE中执行此操作，那么您可以使用以下命令：

  let d：Dining = Dining.make（blah blah）
  

失败 - 它认为d将是一个房间， 不是用餐 。

所以你所有的代码看起来都是这样的：

  let d = Dining.make（blah blah）as！餐馆
  

这很吸引人。如何解决？

---

注意只要TBC的解决方案是使静态为通用的，而不像MartinR在这里的答案 https://stackoverflow.com/a/33200426/294884 下面答案中的代码示例

解决方案

我不喜欢提供我自己的答案，但解决方案是......

所以问题是，在编辑时间

  let d = Dining.make（）
  

不起作用，您必须这样做

  let d = Dining.make（）as！餐厅
  

（它 在编译时工作 ，d变成餐饮：它在编辑时不工作。）

所以解决方案是

  static func make（） - >房间{
 let emplacedAndSetup = self.instantiate（）
 return emplacedAndSetup 
} 
  

变为

 静态func make< T：Rooms>（） - > T {
 let emplacedAndSetup = self.instantiate（）as！ T 
 return emplacedAndSetup 
} 
  

这就是它。

注意 - 完全可能 AppzForLife 的解决方案有效并且/或者更适合作为通用目的UIViewController auto-instantiator ，但这是问题本身的答案。

Consider a base UIViewController class...

class Rooms: UIViewController {
    class func instantiate()->Rooms {
    }

    static func make()->Rooms {
        let emplacedAndSetup = self.instantiate()
        // various kodes here
        // very likely put s.view somewhere
        return emplacedAndSetup
    }

    sundryOtherFunctionality()
}

(Note the self. before instantiate() which seems to be necessary to get "that" instantiator.)

Each subclass knows its own storyboard ID to how use to instantiateViewController:

class Dining: Rooms {
    override class func instantiate()->Dining { // returns a "Dining"
        let d = stbd.instantiateViewController(
            withIdentifier: "Some Specific Scene") as! Dining
        return d
    }
}
class Bath: Rooms {
    override class func instantiate()->Bath { // returns a "Bath"
        let b = stbd.instantiateViewController(
            withIdentifier: "Some Other Scene") as! Bath
        return b
    }
}

You can do this,

let d  = Dining.make()
let r  = Bath.make()

The only minor problem is, it returns the base class. BUT SEE BELOW. So in practice you have to

let d  = Dining.make() as! Dining
let r  = Bath.make() as! Bath

Is there a way to modify the static make so that indeed Dining.make() would return a Dining and Bath.make() would return a Bath?

( @Hamish has pointed out that one could use an init and Self pattern, Method that returns object of type which was called from However, I think that's not possible due to the instantiateViewController. )

---

So. Say you have code like

let d = Dining.make(blah blah)

in fact. At run time, d does become a "Dining", not a "Room"

that's fantastic.

But. If you do this in the IDE

let d:Dining = Dining.make(blah blah)

it fails - it thinks d is going to be a Room, not a Dining.

So all your code has to look like this:

let d = Dining.make(blah blah) as! Dining

which sucks. How to fix?

---

Note just TBC the solution is to make the static a generic, rather as in MartinR's answer here https://stackoverflow.com/a/33200426/294884 Example code in answer below.

解决方案

I don't like to provide my own answer, but the solution is ..

So the problem is, at editor time

let d = Dining.make()

"doesn't work", you have to do this

let d = Dining.make() as! Dining

(It DOES work at compile time, d becomes a Dining: it doesn't "work" at editor time.)

So the solution is

static func make()->Rooms {
    let emplacedAndSetup = self.instantiate()
    return emplacedAndSetup
}

becomes

static func make<T: Rooms>()->T {
    let emplacedAndSetup = self.instantiate() as! T
    return emplacedAndSetup
}

So that's it.

Note - it's entirely possible AppzForLife's solution works and/or is better as a general purpose "UIViewController auto-instantiator", but this is the answer to the question per se.

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