class NewClass: OldClass

class NewClass
   obj: OldClass
   method1(x) { obj.method1(x) }
   method2(x) { obj.method2(x) }    
   method3(x) { obj.method3(x) }

class Example {
  var p: String by Delegate()
}
...
class Delegate {
  operator fun getValue(thisRef: Any?, property: KProperty<*>): String {
    return "$thisRef, thank you for delegating '${property.name}' to me!"
  }
 
  operator fun setValue(thisRef: Any?, property: KProperty<*>, value: String) {
    println("$value has been assigned to '${property.name} in $thisRef.'")
  }
...
val e = Example()
println(e.p)

Example@33a17727, thank you for delegating ‘p’ to me!

type
  IWorker = interface
    procedure DoWork();
  end;
  TWorker = class(TInterfacedObject, IWorker)
    procedure DoWork();
  end;

  TBoss = class(TInterfacedObject, IWorker)
    property Subordinate: IWorker read GetSubordinate implements IWorker; //  босс делегирует реализацию IWorker подчиненному 
  end;

interface IWorker {
  fun doWork()
}

class Worker() : IWorker {
  override fun doWork() {}
}

class Boss(val subordinate: IWorker) : IWorker by subordinate

Б>class NewClass
Б>   obj: OldClass
Б>   method1(x) { obj.method1(x) }
Б>   method2(x) { obj.method2(x) }    
Б>   method3(x) { obj.method3(x) }
Б>

package NewClass;

has obj => (
    is      => 'rw',
    isa     => InstanceOf[OldClass],
    handles => [qw(method1 method2 method3)],
);

struct Foo
{
    int baz = 4;
    int get() { return 7; }
}

class Bar
{
    Foo foo;
    alias foo this;
}

void main()
{
    auto bar = new Bar;
    int i = bar.baz; // i == 4
    i = bar.get(); // i == 7
}

type Parent struct {
  a, b int
}

type Child {
  Parent
  c, f bool
}