Object-oriented programming (OOP) design patterns are constructed at least partially by delegating their behaviors to preconstructed OOP patterns to implement the behaviors. A new OOP pattern having one or more behaviors is defined. Each of at least one of the behaviors is delegated to a preconstructed OOP pattern, the preconstructed OOP pattern therefore implementing the behavior. The new OOP pattern is thus constructed at least partially by delegating at least one of its behaviors to the preconstructed OOP patterns. Delegating a behavior to one of the preconstructed OOP patterns can be accomplished within a graphical user interface (GUI). Graphical representations of the new OOP pattern and of the preconstructed OOP patterns are displayed. Dragging the graphical representation of a selected preconstructed OOP pattern onto the graphical representation of the new OOP pattern causes a behavior of the new OOP pattern to be delegated to the selected preconstructed OOP pattern.