Swift nonmutating setters. an Oxymoron?

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While going through Xcode 10.1 release notes I stumbled upon a very unfamiliar term “nonmutating setters”. Inquisitiveness had the best of me and I spent time reading about it and implementing examples. Here is the jest for you

  • nonmutable setters cannot be used within Classes or protocol bound classes
  • nonmutable setters do not mutate instance
  • nonmutable setters have side effects which go beyond the instance

Example of a nonmutating setter and a use

enum ExampleEnum:String{
    case URL,UserName
    var value:String{
            return UserDefaults.standard.value(forKey: self.rawValue) as? String ?? ""
        nonmutating set(newValue){
            UserDefaults.standard.set(newValue, forKey: self.rawValue)

//It can be used as 
 ExampleEnum.UserName.value = "yoooo"


A pat on the back !!