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Abstract

A visual development system is described which provide 'method pointers' allowing a developer/user to achieve delegation between objects programmatically as well as visually. Delegation 'binds' an event source with an event handler. This binding is directly supported within the programming language of the system. Using a simple assignment statement, the user can assign a handler of one object (i.e., delegated-to object) to the method pointer of another object (i.e., delegated-from object). A delegation through assignment leads to not only the address of the method being copied but also the address of the delegated-to object (i.e., 'this' pointer) being copied into the method pointer. The method pointer, when called, can invoke the pointed-to method on that (delegated-to) object, complete with the context (e.g., local data) of the object. The object knows about itself and, thus, can provide the appropriate context. In this fashion, the system allows the user to easily control object behavior through delegation, whether the user is working in a visual environment or a programming environment (or switching back and forth between each).

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