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In the first three days, you learned about the concepts of object technology and received a primer on object-oriented programming. Today, you will take your learning a step further. You will learn how to construct actual Visual Basic code from the simple sequence diagrams you created on Day 2, Fundamental Object-Oriented Analysis. |
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Explaining OOP's Role in Solution Development |
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The role of object-oriented programming is to provide you with a way to implement a particular design structure of collaborating class instances. This design structure is typically elaborated in a mix of class models, interaction diagrams such as sequence and collaboration diagrams, and state diagrams. Very little significant decision-making about the architecture of an application should occur while you're doing object-oriented programming. In fact, the more significant decisions that are made during the construction phase (synonymous with OOP) of development, the less sound the architecture. By significant is meant any decision that affects domain classes and key design patterns. There is some flexibility in making decisions about design patterns because these types of structures are not seen by the user (although great changes to them can affect the application's performance, which the user can complain about). Even domain classes are part of the user's vocabulary. What's more, they are the most valuable assets within the software that the customer (or even yourself as an entrepreneur) will want to reuse again and again. Thus, object-oriented programming should be for purely implementation purposes and not design, if possible. |
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After reading the first three chapters, you should have a good understanding of classes. Let's reinforce that knowledge and build on it with concrete programming examples. Just as a reminder, classes are clearly defined abstractions from complex conceptual entities discovered in the real world. Each class exhibits distinguishable characteristics, including attributes and behavior. |
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A Visual Basic class follows the same conventions of typical object-oriented classes, except that its internal implementation can't be inherited. A Visual Basic class can inherit the interface of another but is required to implement it. With Visual Basic classes, you have the flexibility of creating property methods in one of two ways: regular functions and subs, or built-in PropertyGet and Let methods (with an optional PropertySet |
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