为什么我不能将Objective-C对象中的KVC用于Swift属性？

My team has decided that new files should be written in swift, and I am seeing an odd problem with using KVC in an Objective-C object to set a property on a Swift object.

我的团队已决定新文件应该用swift编写，我发现在Objective-C对象中使用KVC在Swift对象上设置属性有一个奇怪的问题。

My Objective-C sets a property like so: [textObject setValue:0.0 forKey:@"fontSize"]

我的Objective-C设置了如下属性：[textObject setValue：0.0 forKey：@“fontSize”]

My Swift object (textObject) has a custom setter/getter for this property.

我的Swift对象（textObject）具有此属性的自定义setter / getter。

   var fontSize: CGFloat? {
      get {
         return internalTextGraphic?.fontSize 
      }
      set {
            internalTextGraphic?.fontSize = newValue
      }
   }

However, if I set a breakpoint in the set, it never gets hit.

但是，如果我在集合中设置断点，它永远不会被击中。

I have Objective-C objects that also get this same call, and I just implement -setFontSize, and the execution enters properly.

我有Objective-C对象也得到同样的调用，我只是实现-setFontSize，并且执行正确进入。

Why can't I seem to get into my set method through -setValueForKey? I have 100% confirmed the textObject is exists and is the correct type.

为什么我似乎无法通过-setValueForKey进入我的set方法？我100％确认textObject存在且类型正确。

EDIT:
Martin R is correct, I had to make the type a non-optional. This is my working code:

编辑：马丁R是正确的，我不得不使类型不可选。这是我的工作代码：

   var fontSize: CGFloat {
      get {
         var retFontSize: CGFloat = 0.0
         if let fontSize = internalTextGraphic?.fontSize {
            retFontSize = fontSize
         }
         return retFontSize
      }
      set {
         if let textGraphic = internalTextGraphic {
            textGraphic.fontSize = newValue
         }
      }
   }

1 个解决方案

#1

The reason is that a Swift optional struct or enum (in your case CGFloat?) is not representable in Objective-C (and you won't see that property in the generated "Project-Swift.h" header file). That becomes more obvious if you mark the property explicitly with @objc, then you'll get the error message

原因是Swift可选的struct或enum（在你的情况下是CGFloat？）在Objective-C中是不可表示的（你不会在生成的“Project-Swift.h”头文件中看到该属性）。如果使用@objc显式标记属性，那么这将变得更加明显，然后您将收到错误消息

error: property cannot be marked @objc because its type cannot be represented in Objective-C

If you change the property type to the non-optional CGFloat then KVC works as expected. It would also work with an optional class type, such as NSNumber?.

如果将属性类型更改为非可选的CGFloat，则KVC将按预期工作。它也适用于可选的类类型，例如NSNumber？。