Object-Oriented Environments
Offering some much-needed competition to distributed systems, object-oriented applications have their foundation based in a completely different approach to information systems and processes — one based on objects and reusability (yes, it really is more environmentally friendly to recycle old computer code). Object orientation is an entire computing universe, comprising object-oriented analysis, design, programming, and even databases.
The object-oriented religion is based on a fundamental principle: Objects, after they’re written, can be reused again and again, thereby making the enterprise’s entire software development effort more and more efficient over time.
Object orientation is known as OO, pronounced oh-oh (not uh-oh).
An object is encapsulated, which means that the inner workings of an object are hidden and can remain so. Objects communicate with each other by using messages. When an object receives a message, it performs whatever function it was designed to do, which is its method.
An object that’s running is an instance. The process of starting an instance is instantiation. But an instance can also refer to an object that’s a member of a class of objects. For example, a chocolate cake recipe is a method, and a cake that has been baked using the recipe is an instance of the recipe.
As you can see, OO has quite a vocabulary, and you haven’t seen half of it yet. But now you can be sure that when you hear a couple of guys talking about someone’s objects (ahem), you have the secret decoder ring to know that they’re computer-science types, probably even hip web developers.
If you’re tiring of reading about OO terms buried in paragraphs, here they are in a little glossary:
Behavior: The results of an object having received a message.
Class: In his book Business Engineering with Object Technology (Wiley), author David Taylor describes a class as “a template that defines the methods and variables to be included in a particular type of object.” The class itself contains the common methods and variables, and objects in the class contain only those characteristics that make them unique. OO also includes subclasses (parts of a class) and superclasses (collections of classes).
An example of a class is the class Cake. From this class, an object called Chocolate Cake can be created. Also, objects such as Bundt Cake, Carrot Cake, Layer Cake, and Cup Cake are objects in the class Cake. The methods associated with these objects describe the unique details of each type of cake. The method associated with each type could be a recipe for making a cake or for eating a cake (we prefer the latter).
Class hierarchy: The tree structure of a collection of objects and classes.
Delegation: What happens when an object receives a message requesting a method that it doesn’t have. The object delegates the message to the object that does contain the requested method.
Encapsulation: The packaging of an object. Everything inside the object is hidden, or encapsulated.
Inheritance: An object that gets some of its characteristics from a class. An object inherits characteristics from the class when it’s instantiated. (It doesn’t have to wait for the class to grow old and die.)
Instance: A particular object that’s a member of a class.
Message: How objects communicate with one another. A message contains the name of an object to which it wants to communicate, the method it should perform, and usually one or more parameters. The object sending the message is the sender; the object receiving it is the receiver.
Method: The procedure (code) contained in an object.
Multiple inheritance: When an object or class inherits characteristics from more than one class.
Object: The basic unit in OO.
Polyinstantiation: The process of developing one object from another object, but with different values in the new object.
Polymorphism: Taylor describes this as “the ability to hide implementation details behind a common message interface.” This permits new objects to be added to a system without having to rewrite existing procedures.