% set a [Delegator new] +% $a operation +default implementatiton
package req nx + +nx::Class create Delegator { + + # The class Delegator has a property named "delegatee" which is an + # object: + + :property delegatee:object + + # The method "operation" decides, whether it deletates the action to + # another object, or it performs the action itself. + + :public method operation {} { + if {[info exists :delegatee]} { + ${:delegatee} operation + } else { + return "default implementatiton" + } + } +} + +nx::Class create Delegatee { + + # The class "Delgatee" might receice invocations from the class + # "Delegator" + + :public method operation {} { + return "delegatee implementatiton" + } +}
Create a Delegator, which has no delegatee defined. Therefore
delegator performs the action by itself, the default implementation.
% set a [Delegator new] +% $a operation +default implementatiton
Now, we set the delegatee; therefore, the delegatee will perform
the action.
% $a configure -delegatee [Delegatee new] +% $a operation +delegatee implementatiton