[swift-evolution] constant var

Magnus Ahltorp map at kth.se
Thu Dec 14 03:38:09 CST 2017

> 14 Dec. 2017 17:52 Inder Kumar Rathore . via swift-evolution <swift-evolution at swift.org> wrote:
> class MyClass {
>   private var myDict = [String : String]()
>   func addMemebr() {
>     self.myDict["key"] = "value" // Ok for me
>   }
>   func anotherFunc() {
>     self.myDict = [String : String]() // Not okay for me, I don't want any code to do this within the class
>   }
> }

But in Swift, since myDict is a Dictionary, it is *one* value, so it doesn't make sense to allow one but not the other. Also, since it is one value, you will not be able to detect the difference between setting a part of a dictionary and the whole dictionary. If Dictionary had been a class, there would be a non-changing reference, but there isn't in this case. Conceptually, the whole dictionary is copied every time you set it or assign it.


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