0.5 Xna0108-inheritance in c#  (Page 6/7)

The program output

The code in Listing 3 produces the first five lines of output text shown in Figure 1 .

The remaining code

You can view the remaining code in the Driver class and the code in the Airplane class in Listing 4 . If you understand my explanation of Listing 1 , Listing 2 , and Listing 3 above, you should have no difficulty understanding the behavior of the code inthe Airplane class and the remaining code in the Driver class.

No sharing of properties

There is an important point to remember, however. Even though the Balloon and Airplane classes each inherit the range and altitude properties from the Airship class, objects instantiated from the Balloon and Airplane classes do not physically share these two properties. Instead, each object has its own copy of the range property and its own copy of the altitude property. The only thing shared by the two objects is part of the blueprint from which each object is constructed.

Basically there is no sharing of anything among objects until the static keyword shows up and at that point, some sharing does take place. The use of the static keyword is a topic for a future module.

Run the program

I encourage you to copy the code from Listing 4 . Use that code to create a C# console project. Compile and run the project. Experiment with the code,making changes, and observing the results of your changes. Make certain that you can explain why your changes behave as they do.

Run my program

Click here to download a zip file containing my version of the program. Extract the folder named Airship01 from the zip file and save it somewhere on your disk. Start Visual C# 2010 Express and select Open Project... from the File menu. Navigate to the project folder and select the file with the extension of .sln . This should cause the project to open and be ready to run or debug as described in the earlier module titled Getting Started .

Summary

In this module, you learned how one class can extend another class and inherit all of the properties, events, and methods defined in that class and allof its superclasses. You learned that even though a class may be extended into another class, it remains viable and can be instantiated in its own right. Youlearned that inheritance is hierarchical with the overall hierarchy being rooted in a class named Object . You learned that C# does not support multiple inheritance. You learned about the ISA and HASA relationships.

Miscellaneous

This section contains a variety of miscellaneous information.