Re: Code reuse
From: Kevin Spencer (kspencer_at_takempis.com)
Date: 05/24/04
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Date: Mon, 24 May 2004 13:29:23 -0400
You asked specifically about 2 things: Inheritance and Interfaces. Let's
start with Inheritance, as that is the easiest to understand.
In Object-oriented programming, you have classes that encapsulate
functionality, rather than functions existing outside of any class. In
procedural programming, you have what is called function libraries, for
re-usable functions. Function libraries are DLLs, but they contain only
functions, not classes. In OOP, you have classes that encapsulate
functionality. For re-usability, you can use inheritance. For example, let's
talk about System.Web.UI.WebControl. All WebControls inherit this class.
Why? Because they all have some things in common. By creating a base class
that contains all the functionality that is shared by these classes, you
re-use the base class and its functionality in each derived class. For
example, all WebControls have an Attributes property, because all HTML
objects have attributes. By encapsulating this in a base class, you don't
need to re-write the code for each derived class, and if there is a need to
change this functionality, you change it in one place (the base class) and
all derived classes inherit that functionality.
Interfaces are a bit different. They define a "contract" if you will, that
specifies certain characteristics that are required by any class that
implements the Interface. These characteristics are either fields,
properties, or methods, which must have a certain signature. For example,
when creating a Server Control that implements IPostBackEventer, you must
implement a method called "RaisePostBackEvent." Why? Because, in order for
the class to handle PostBack events, it must have a method which can be
called from outside the class, which conforms to the signature of the
RaisePostBack method in the IPostBackEventHandler contract. In other words,
there is an external dependency in the architecture, which expects to find a
method with that signature.
Does that help?
-- HTH, Kevin Spencer .Net Developer Microsoft MVP Big things are made up of lots of little things. "Simon" <sh856531@microsofts_free_email_service.com> wrote in message news:#4gk1ILQEHA.3012@TK2MSFTNGP09.phx.gbl... > Hi all, > > > > I'm hoping that some of you clever chaps could offer me some advice on code > reuse. > > > > You see, whenever I make applications, I typically only find very limited > scope for code reuse. I also only find limited use for inheritance. For > example, the various types of users that my system might have to deal with. > > > > I'm wondering if anyone could give me some tips on how to identify areas of > my design that could be reusable, where I can use inheritance and where to > use interfaces. I've read all the books that talk about why these things are > important but very few of them show you how to do it in the real world. > > > > If anyone could point me to some online resources on this then that would be > great. I could also do with a couple of books on how to spot reusable > aspects of my designs and so on. > > > > Any help would be great > > > > Thanks all > > > > Simon > >
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