Delegation

18 May 2024 . kotlin .

Explicitly delegation

Supported by all object-oriented language by passing a delegate object (the one to be implemented) to a delegating object (the one that will implement delegate object).

interface delegation 
{
    fun mymessage()
}
  
class delegationimplementation(val y: String) : delegation
{
    override fun mymessage() 
    { 
        print(y)
    }
}

fun main() 
{
    val b = delegationimplementation("\nWelcome, GFG!")
      
    b.mymessage()
}

Implicit delegation

Require language-level support: in Kotlin, use keyword by .

interface delegation 
{
    fun mymessage()
    fun mymessageline()
}
  
class delegationimplementation(val y: String) : delegation
{
    override fun mymessage() 
    { 
        print(y)
    }
    override fun mymessageline() 
    { 
        println(y)
    }
}
  
class Newfeature(m: delegation) : delegation by m
{
    override fun mymessage() 
    {
        print("GeeksforGeeks")
    }
}
  
fun main() 
{
    val b = delegationimplementation("\nWelcome, GFG!")
      
    Newfeature(b).mymessage()
    Newfeature(b).mymessageline()
}

Output

GeeksforGeeks
Welcome, GFG!

Advantages:

Multiple interfaces can be implemented with the help of existing ones.
Used to add new features and values to current implementations.