Access a struct property by its name as a string in Swift

Question

Let\'s say I have the following struct in Swift:

struct Data {
   let old: Double
   let new: Double
}

Now I have a c

Answer 1

You're looking for key-value-coding (KVC) that is accessing properties by key (path).

Short answer: A struct does not support KVC.

If the struct is not mandatory in your design use a subclass of NSObject there you get KVC and even operators like @avg for free.

class MyData : NSObject {
  @objc let old, new: Double

  init(old:Double, new:Double) {
    self.old = old
    self.new = new
  }
}

let myDataArray : NSArray = [MyData(old: 1, new: 3), MyData(old:5, new: 9), MyData(old: 12, new: 66)]

let averageOld = myDataArray.value(forKeyPath:"@avg.old")
let averageNew = myDataArray.value(forKeyPath: "@avg.new")

Edit: In Swift 4 a struct does support Swift KVC but the operator @avg is not available