Transcript PowerPoint

IMAT1604 Visual Web Development
What is an Object Anyway?
 What is a word?
 Think about the following word…
Shop
 What springs to mind?
A Specific Shop
The act of shopping…
Creating Instructions
 A word on its own isn’t much use to us however when
we combine it with other words we can create
instructions.
 “I want you to go to the shop and get me a tin of peas.”
Words are Really Just Symbols
 What is this?
What if we add other symbols?
 Traffic lights and words on a page are all the same they
are all symbols that we look at and assign meaning.
What is Programming?
 Programming is about using words and symbols to
communicate with a Computer
 As with our example above we use words / symbols to
create instructions or functions that the computer will
follow and perform some task.
 Functions are organised into classes – text files
Who is this?
 More to the point why is she so irritating?
 We need to use the right words correctly
Most of us end up feeling more like
this...
The Importance of Vocabulary
“Shop, street, road, post box, lamp post, post code, house, flat,
house number, left, right ahead, distance, time, street sign,
landmark.”
 These words make up the vocabulary of the streets and
roads. We are familiar with these words and can easily
make up instructions (functions) using these words.
“You want to walk down that street for 10 meters then turn left
at the post box. You will then see a sign to the railway
station. Follow that sign for 5 meters and the shop is on the
left.”
Computer Programming
Introduces a new Vocabulary
“Class, object, assignment, sequence, variable, RAM,
parameter, data type, function, method, property,
selection, sequence, integer, string.”
The Computer Programmer
 The person who knows how to write the correct words
/ symbols to tell the computer what to do
 Computers copy and process data
 Data is made of binary numbers
 Nobody really likes binary
 We need a set of commands to control data
First Look at Some C# Code
 What is wrong with this?
The Problem
 Computers are really fussy
 Spotting errors can be difficult at first
 This gets easier with practice
 Take a look at the following…
Int32 Name;
Name();
“Name”
.Name
//Name
(Name)
-
Variable
Function
A string of letters
A method or a property (Probably a property)
A comment
A parameter
New Terms to Understand
 Function
 Method
 Property
 Class
 Instantiation
 Object
Functions
 “A function is sequence of words and symbols that
instruct the computer to perform a single action on
some data well.”
Methods and Properties
 Method
 A function that acts on the data in some way
 E.g. Multiply
 Property
 A function that allows us to find out something about
the data or to set some aspect of it.
 E.g. Count
 (This will be confusing at first!)
Classes
 A class is a text file that contains related functions making them
easier to manage
 Classes are like recipe books
 Recipe books dedicated to specific regions
 Classes dedicated to specific sets of functionality
 A student manager class might contain…
 Methods



.AddStudent
.UpdateStudent
.DeleteStudent
 Properties


.Count
.HighestStudentGrade
So what is an Object Anyway?
 An object may be thought of as simply a word that
means something to the computer
 The object in this code is MyStudents
 Made up by the programmer
 Associates the word with the class file clsStudents
 Allowing us to access the function/method AddStudent
Instantiation
 Stuff in green called comments
 Create an object MyCompter referencing the code in
the class file clsComputer
 Invokes the function/method TurnOff
 Instantiation is the act of creating an object
Summary
 Programming is the act of writing lists of words that control the data in
the system
 We need a system for writing lists of instruction for the computer that
makes reasonable sense to human beings
 We also have some key words for you to start getting to grips with…
 Function
 Property
 Method
 Class
 Object
 Instantiation
A function is sequence of words that instruct the
computer to perform a single action on some data
well
A property is a function that tells us about or sets
some aspect of the data
A method is a function that changes the data in
some way
A class is a collection of related functions in a text
file
An object is a word that references the code in the
associated class
The process of linking an object to a class