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Expose the interface and hide the implementation

As in the steering mechanism for a car, a common approach in OOP is to "hide the implementation" and to "expose the interface" through encapsulation.

Inheritance example

Another important aspect of OOP is inheritance. Let's form an analogy with the teenager who is building a hotrod. That teenager doesn't normally start witha large chunk of steel and carve an engine out of it. Rather, the teenager will usually start with an existing engine and make improvements to it.

OOP lingo

In OOP lingo, that teenager extends the existing engine, derives from the existing engine, inherits from the existing engine, or subclasses the existing engine (depending on which author is describing the process) .

Just like in "souping up" an engine for a hotrod, a very common practice in OOP is to create new improved classes and objects by extending existing classdefinitions.

Extending the Game class

When you use Visual C# to create a new XNA game project, the IDE creates skeleton code for a new class. As you will learn later in this course, it isthen up to you to put some meat on the skeleton and turn it into a game. The first executable statement in the skeleton code is shown in Listing 1 .

Listing 1 . Extending the Game class.

public class Game1 : Microsoft.Xna.Framework.Game

The code in Listing 1 is the first executable statement in the definition of a new class named Game1 (or whatever name you give the new project) . The definition of the new class extends an existing class named Game , which resides in the Microsoft.Xna.Framework namespace. The existing class named Game , is the main controller for your new game. I will have much more to say about the Game class in a future module.

Reuse, don't reinvent

One of the major arguments in favor of OOP is that it provides a formal mechanism that encourages the reuse of existing programming elements. One of themottos of OOP is "reuse, don't reinvent."

Polymorphism example

A third important aspect of OOP is polymorphism. This is a Greek word meaning something like one name, many forms . This is a little more difficult to explain in non-programming terminology. However, we will stretch our imaginationa little and say that polymorphism is somewhat akin to the automatic transmission in your car. In my Honda, for example, the automatic transmissionhas four different methods or functions known collectively as Drive (in addition to the functions of Reverse, Park, and Neutral) .

Select Drive to go forward

As an operator of the automobile, I simply select Drive (meaning go forward) . Depending on various conditions at runtime, the automatic transmission systemdecides which version of the Drive function to use in every specific situation. The specific version of the function that is used is based on the currentconditions (speed, incline, etc.) . This is somewhat analogous to what we will refer to in a subsequent tutorial module as runtime polymorphism.

Object-oriented programming vocabulary

OOP involves a whole new vocabulary (or jargon) which is different from or supplemental to the vocabulary of procedural programming.

Questions & Answers

find the 15th term of the geometric sequince whose first is 18 and last term of 387
Jerwin Reply
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
virgelyn Reply
hmm well what is the answer
Abhi
how do they get the third part x = (32)5/4
kinnecy Reply
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
ninjadapaul
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
ninjadapaul
I don't understand what the A with approx sign and the boxed x mean
ninjadapaul
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
ninjadapaul
oops. ignore that.
ninjadapaul
so you not have an equal sign anywhere in the original equation?
ninjadapaul
hmm
Abhi
is it a question of log
Abhi
🤔.
Abhi
Commplementary angles
Idrissa Reply
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
hii
Uday
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Xna game studio. OpenStax CNX. Feb 28, 2014 Download for free at https://legacy.cnx.org/content/col11634/1.6
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