Using a string parameter to describe class property

Question

I want to write a function that takes a string and then prints the value of the class property with that name. In practice, there would be more than one property to choose form. For example...

class Apple{
  var juiciness : Int = 0
  init(juiciness: Int){
    self.juiciness = juiciness
  }
}

var myApple(juiciness : 10)

func printValue(property : String){
  print(Apple.property) // <-- I want to use the string to choose a property
}

Obviously, I can't do this code but I know there has to be a better solution than just I series of if statements.

http://stackoverflow.com/questions/24138705/access-properties-via-subscripting-in-swift — chengsam, Mar 07 '17 at 02:55
Do you *really* want to take a string? This would be much better implemented with a closure. — Hamish, Mar 07 '17 at 03:04
For future reference, this sort of functionality is called "reflection" — Alexander, Mar 07 '17 at 03:53
It doesn't need to be a string. How would I do it with a closure? — spogatetz, Mar 07 '17 at 19:51

score 1 · Answer 1 · answered Mar 07 '17 at 03:03

1

Apple has done this for you. It is known as key-value observing(KVO). Try the following code in the playground:

let label = UILabel()
print(label.value(forKey: "font"))

Your own class can support KVO by inheriting from NSObject:

class YourClass: NSObject{ ... }

answered Mar 07 '17 at 03:03

LinShiwei

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17

Can I inherit from NSObject as an NSManagedObject? – spogatetz Mar 07 '17 at 03:06
1

@spogatetz NSManagedObject is a subclass of NSObject. You can simply inherit from NSManagedObject. – LinShiwei Mar 07 '17 at 03:33

Using a string parameter to describe class property

1 Answers1