Beginning Object-Oriented Programming with C# by Jack Purdum

Author:Jack Purdum
Language: eng
Format: epub, pdf
Publisher: John Wiley & Sons
Published: 2012-10-26T16:00:00+00:00

Always Call the Default Constructor

You might be asking yourself: “Why bother calling the default constructor? If you never use the content of current, who cares?” Well, given the way clsDates is written presently, current isn't used, so it really doesn't matter. However, that does not mean you won't add code later on that does assume a default state for current.

More important, calling the default constructor gets you into the coding habit of establishing a “base state” for the object. Not starting all objects with the same base state may cause problems later. For example, you might be writing some form of a database class in which the default constructor creates a connection to the database. If an overloaded constructor didn't also establish that database connection, perhaps other methods in the class could not perform their functions properly.

If you do write a constructor that has parameters, you can no longer call the default constructor that has no parameters. The only way you can call a parameterless constructor once you have created a contructor with parameters is to explicitly write your own parameterless constructor. That is, the “no-code” default constructor no longer exists and you must supply your own.

Just as you've seen so many times before, the Initialization Step of the Five Program Steps creates the base environment in which the program code is to perform. Calling a constructor is similar to the Initialization Step for a program but viewed in the more narrowly defined context of a method. That is, the constructor establishes the environment in which a specific object is to exist and perform. Therefore, it is always a good idea for all overloaded constructors to call the default constructor so that the base state of the object can be safely assumed.

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