Methods in Protocols

Question

I am very new to protocol oriented programming ,so my question may be very easy.

I intend to define a Cloneable protocol which has a clone() method. This method returns the object whose contents are same as contents of the object which invoke clone() method. Thus, return type of clone() method must adjust to the class adopting Cloneable protocol.

protocol Cloneable{

   func clone() -> AnyObject
}


public final class Circle : Cloneable{


   private var radius : Double
   private var area : Double
   private var perimeter : Double


   public init( radius : Double ){
      self.radius = radius
      area = PI * radius * radius
      perimeter = 2 * PI * radius
   }

   public convenience init(){
      self.init( radius : 1.0 )
   }

   func clone() -> Circle{
      return Circle( radius : self.radius )
   }
}

I get error that Class Circle does not conform to Cloneable protocol. It wants me to change AnyObject with Circle. If I do that, How can this protocol be used for all classes ?

score 0 · Accepted Answer · answered Aug 17 '17 at 06:59

0

Change this code -

func clone() -> Circle{
   return Circle( radius : self.radius )
}

to this code -

 func clone() -> AnyObject {
    return Circle( radius : self.radius )
 }

answered Aug 17 '17 at 06:59

Abhishek Jain

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It is very reasonable – Goktug Aug 17 '17 at 07:01
The problem with this approach is that you always have to cast the return value: `let circle2 = circle1.clone() as! Circle` – Martin R Aug 17 '17 at 07:06
This is the nature of Generic protocol. – Abhishek Jain Aug 17 '17 at 07:09
Have a look at https://stackoverflow.com/questions/25645090/protocol-func-returning-self for solutions avoiding this problem. – Martin R Aug 17 '17 at 07:13

Methods in Protocols

1 Answers1