Introduction to the Object-Oriented Approach

Programming Object-Oriented Programming (OOP) is one of the popular methodologies in software development. It offers a powerful model for creating computer programs. It speeds the program development process, improves maintenance, and enhances reusability of programs. This chapter introduces the object-oriented methodology and discusses the concepts of objects, classes, messages, and methods. It provides an overview of the phases involved in object-oriented analysis and design. Details Object-Oriented Methodology Object-orientation is a software development methodology that relates to the real-world system. An object is the main concept involved in this methodology. An object is the representation of a real-world entity or concept. For example, an employee, a window, a car, or a bird can be represented as objects. You can think of an object-oriented model as a collection of objects and their relationship with each other. Objects An object literally means a 'material thing' that can be presented physically. In other words, an object is a touchable entity that may show some well-defined behavior. For example, consider the following statements in context of a tennis ball: A tennis ball is a touchable entity, with a visible boundary in physical terms. A tennis ball has a specific defined purpose (such as bouncing). A tennis ball can be acted upon (such as can be hit with a racquet or can be tossed around). But the definition of an object is not limited to merely something that can be seen, held, and touched, such as a tennis ball or a chair. For the purpose of software development, you can define non-touchable things also in the form of objects. For example, in a car racing video game, the car is an object. You can drive the car, turn the car, or stop the car when needed. There are no visible boundaries when you are playing a video game. Here, everything is abstract. Characteristics of the Object-Oriented Approach Realistic Modeling Reusability Flexibility to Change Existence as Different Forms Phases of Object-Oriented Methodology Before the actual development of any product, important steps, such as analysis and design need to be performed. The following phases are involved in the object-oriented methodology: The Analysis phase The Design phase The Implementation phase Consider an aircraft manufacturing factory where a new aircraft is being assembled and several competent engineers and workmen are working with specialized tools. Can you visualize them working purely on what they feel, grabbing the tools, and sitting down to work immediately? Or, do you see them working according to a detailed design on which they have spent hundreds of hours, and finally constructing the aircraft based on the specified design. For the safety of millions of people who fly every day, it is recommended to use a detailed design. After all, it is comforting to know that a lot of thought has gone into first making a model design on paper and then translating the design into the physical aircraft. The same holds true for almost any item that is constructed. Similarly, fashion designers put pen to paper before cutting the fabric with scissors and Architects draw layouts of buildings on blueprints before the bricks are laid. The development of software follows the same approach. The software industry still relies mainly on the informal paper-and-pencil approach in the initial development phases. This paper-and-pencil approach is termed analysis and design. To analyze and design a system, you need to build a model of the system. This model is simpler than the system that is finally constructed. All the practical aspects of building a system for the real world cannot be reflected in the design. However, this does not lessen the importance of the design.

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