Transcript New Kogod Powerpoint Template

ITEC 334 Fall 2011
Online (Business) Application Development
Topic: Programming Concepts
Professor J. Alberto Espinosa
Agenda
• Object Orientation
• Programming Fundamentals
2
Object
Orientation
(OO)
3
Object-Orientation (OO)
The Idea Behind OO
• Computer applications are the virtual representation of some real
world activity (e.g., buying goods, paying invoices, processing payroll,
etc.)
• The physical world is composed of physical objects (e.g., people,
buildings, automobiles, computers)
• Each physical object has properties or attributes (e.g., size, weight,
age, name) and behaviors (e.g., purchase, enroll, register, paying)
• The idea behind OO is to represent physical objects as virtual
objects in a computer application (e.g., courses, students, orders)
• By recording their properties (e.g., course name, student ID, order no)
and programming their behaviors (e.g., registration, payments, etc.)
• OO programming writing software code by creating, manipulating
and using objects
4
Objects and Classes
• An object is a person, place, event or other thing
• A class is a category or grouping of similar objects
• We say that an object (e.g., Prof. Espinosa) is an
“instance” of a class (e.g., professors)
• An object has:


Attributes (i.e., data; e.g. Courses.Semester)
Behaviors (i.e., programs; e.g., Courses.ModifyCourse( ))
• Keeping attributes and methods in the same
object is a concept known as “encapsulation”
• Another important OO concept is “inheritance”
– Objects inherit all attributes and methods from their class
– Classes inherit all attributes and methods from super-classes
5
Attributes
(or Properties)
•
A class attribute is like a database field (e.g., clientID, instructorName)
•
For example, this command in ASP (we will see this later in the semester)
retrieves database records into an ASP object called “recordset”:
Set rsCust = Conn.Execute("SELECT ClientID, ClientName FROM Clients“)
•
ASP creates this record set object we have named rsCust. This object not
only has all the data retrieved from the SQL query results, but it also contains
other attributes with very useful information provided by ASP, including the
number of fields in the recordset, names of those fields, number of records in
the set and much more: see http://www.w3schools.com/ado/ado_ref_recordset.asp
•
An object attribute can be usually accessed with syntax like object.property
(e.g., student.name)
•
For example, a set of ASP commands like these can access values stored in
fields in the record set rsCust:
MyFirstCustID = rsCust.fields(“ClientID“) .value
MyFirstCustName = rsCust.fields(“ClientName“) .value
6
Behaviors
(or Methods or Operations)
•
Methods or Operations are procedures/programs (written in an OO
programming language) to update, manipulate or query data in object
attributes
•
Some of them apply to a single object in a class (e.g., create, modify,
delete or display data from an object) whereas some others apply over a
range of objects (e.g., list a range of products, print course catalog)
•
A method or operation can usually be executed with syntax like
object.method( )
•
For example, in ASP (we will see this later in the semester) a command
like conn.Execute( ) is a method available to execute an external
command (e.g., an SQL query).
•
The ( ) is used to pass information to the method,
e.g., conn.Execute(“SELECT * FROM Clients”)
•
The ( ) some times are not needed, e.g., rsCust.MoveFirst
7
Inheritance
• Objects inherit operations and properties from their respective class
• Sub-classes can be created under other classes
• Sub-classes inherit operations and properties from super-classes
• For example, in ASP the Set command creates a sub-class from
another class – e.g., this is the typical set of commands you will use to
get data from an MS Access database:
Set conn = Server.CreateObject("ADODB.Connection“) ‘create a connection object
conn.open “delivery” ‘open a connection to the delivery database (DSN = delivery)
Set rsCust = Conn.Execute("SELECT clientID, clientName FROM clients")
• OO languages are great for programming, but not that great to handle
persistent (i.e., stored) data. In contrast, database programs are not
that great for programming, but they are great at handling persistent
data.
Solution: Store data in databases  retrieve data into objects
 manipulate the objects using an OO language
 store results in database
8
Application Building Blocks
Client-Side Scripting:
ColdFusion
Database:
•JavaScript programming
• Relational Design
• SQL Queries
HTML:
• Hand-coding HTML
• Automatic generation of
HTML code w/scripts
iPhone/Mobile
RSS/XML
PhP/LAMP
Java/JSP
• VB.NET software language we will use to
generate HTML code
AJAX
Server-Side Scripting: ASP.NET
• ASP.NET object manipulation with
SharePoint
WordPress
Other development platforms and software languages:
Perl
C#
Python
Ruby on Rails
HTML 5
9
HTML and the Document Object Model (DOM)
DOM: A convention adopted to represent and access HTML objects
by programs and scripts (particularly useful with JavaScript
10
JavaScript, OO & the Document Object
The Document Object – i.e., the web page you are in, used by JavaScript to interact
with elements of the web page. For example document.write( ) is a method in
JavaScript that writes text in the document object (i.e., the web page being loaded)
Ex1. document.write(“<h1>Welcome to my Web Page</h1>”);
Ex2. text1 = “<h1>Welcome to ”;
text2 = “my Web Page</h1>”;
document.write(text1 + text2);
JavaScript
Example 1
<form name="MyOrder" method="post">
<input type="text" name="Qty“ />
<input type="text" name="Price“ /> etc.
</form>
HTML
<script>
var Q1 = document.MyOrder.Qty.value;
var P1 = document.MyOrder.Price.value;
var total = P1*Q1 ;
</script>
JavaScript
Example 2
11
ASP.NET’s
OO Programming Environment
•
Active Server Pages (ASP.NET) is a Microsoft server-side development
platform available in Microsoft Internet Information Servers (IIS)
•
Essentially, ASP.NET consists of a number of object classes that have
been already developed by Microsoft and made available to developers
like you to facilitate web development
•
These classes have pre-defined properties and pre-programmed
methods to do several things, like: connect to databases, query
databases, access data retrieved with database queries, send HTML text
and tags to web pages, etc.)
•
How to do this? By writing scripts using a scripting language (e.g.,
VisualBasic.NET, Perl, C#) and including commands to manipulate
ASP.NET objects to:
•
•
Access ASP object properties (i.e., data) and
Invoke ASP object methods (i.e., run available programs).
12
Important ASP.NET Objects
1. The Response Object: is the actual response page the web server is generating to
send to the browser – i.e., a “response”
Ex1.
response.write(“<h1>Welcome to my Web Page</h1>”)
Ex2.
text1 = “<h1>Welcome to ”
text2 = “my Web Page</h1>”
document.write(text1 + text2)
2. The Connection Object: to connect to data sources (e.g., databases)
Set conn = Server.CreateObject("ADODB.Connection") ‘create connection object “conn”
conn.open "delivery” ‘open the connection to the database associated with “delivery”DSN
rsOrders = conn.Execute(“SELECT * FROM Orders”) ‘execute a command
3. The Record Set Object: where database data is stored temporarily – e.g., rsOrders
rsOrders.MoveFirst ‘record set object method to go to the first record in the set
OrderNo = rsOrders.fields(“OrderNo”).value ‘the value property stores the data queried
CustomerName = rsOrders.fields(“CustomerName”).value ‘same thing
rsOrders.MoveNext ‘record set object method to move to the next record in the set
For more information on the record set object, see http://www.w3schools.com/ado/ado_ref_recordset.asp
13
Embedding SQL in Scripts
Example 1: embedding a literal SQL command:
rsOrders = conn.Execute(“SELECT * FROM Orders”)
Example 2: embedding a an SQL command in a text variable
QueryString = “SELECT * FROM Orders WHERE CompID = ‘IBM’ ”
rsCompanies = conn.Execute(QueryString)
Example 3: concatenating portions of an SQL command
QueryString = “SELECT * FROM Orders WHERE CompID = ” & “ ‘IBM’ ”
rsCompanies = conn.Execute(QueryString)
Example 4 – concatenating multiple text variables into an SQL command
QStr1 = “SELECT CompID, CompName ”
QStr2 = “FROM Companies ”
QStr3 = “WHERE CompType = ”
QStr4 = “Consulting”
QueryString = QStr1 & QStr2 & QStr3 & “ ‘Consulting’ ”
(or) QueryString = QStr1 & QStr2 & QStr3 & “ ‘ ” & QStr4 & “ ’ ”
14
Programming
Fundamentals
15
Programming Languages
• A program is simply a list of instructions written for the computer
to execute a desired task
• The instructions need to be written in a specific language
• Examples of software languages: Visual Basic, Java, C++
• A script is a small program embedded within a web page,
comingled with HTML, XML, CSS, etc.
• Scripting Languages – specifically created to write scripts
• Examples of Scripting Languages: VisualBasic.NET (VB.NET),
Csharp (C#), Perl, JavaScript (no relationship to Java)
• Structured English: the use of English-like commands to illustrate
programming concepts (useful because it is language neutral) –
we will use it in the next following slides
• All programming languages have:
– Semantics: the set of possible computations that can be
accomplished with the language – i.e., its “meaning”
– Syntax: the rules of how to write programs in that language
16
Language Translation
• Source code: humans write software in languages that only
humans understand – the programs written by humans is called
source code
• Object code: computers can’t execute programs from the source
code – computers only understand “machine language”
• Therefore, source code (the programs we write) need to be
translated into object code (what computers can execute)
• There are 2 general software translation methods:
• Interpretation – source code is translated one line at a time
as needed – e.g., JavaScript (the interpreter is in the browser),
Classic ASP (the interpreter is in the web server)
• Compilation – all source code is translated at once before it
is ever used – e.g., Java (compiled by the programmer),
ASP.NET (compiled by the web server)
17
Variables
• Think of them as containers of data (in memory)
• A variable has a name (e.g., x, Age, Salary) so that the
data in that container can be accessed
• Variable types – e.g. text, numeric, date, logical
• An array  a matrix of variables – e.g., Salary(3)
• Variable assignment:
 x = 4 (store the value of 4 in variable or container x)
 x = x + 1 (take whatever is in x and add 1 to it)
 Salary = 100000 (note that there are no commas in the number)
 Name = “alberto” (note that text data needs delimiters)
 Name = Name + “ espinosa”
 DateToday = now()
18
Variable Declarations
• Some program language require that you initialize or declare
variables before you can use them
• For example:
VB.NET (notice, no need for semicolon):
Dim Name
Name = “Alberto”
JavaScript (notice, it MUST end the command with a semicolon):
Var Name = “Alberto”;
• Dim Salary(3) ‘this creates an “array” which can store 3 salary values:
Salary(0), Salary(1), Salary(2) – confusing, I know – each behave as an
individual variable
• Implicit declarations: some software languages don’t need variable
declarations – they are automatically (i.e., implicitly) declared the
first time they are used in a program
19
Input and Output
• An input is a value entered for the program to process (e.g., Login ID) –
entered by a user or retrieved from another program or database
• An output are the results produced by the program – displayed or printed to
the user or fed to another program or database
Note: ‘ is used to write comments in ASP and VB.NET
Example 1 – Visual Basic
INPUT EmployeeID, Salary
NewSalary = Salary * 1.10
OUTPUT EmployeeID, NewSalary
‘prompt user to enter this data
‘screen display output
Example 2 – ASP
rs = conn.Execute(“SELECT EmployeeID, Salary FROM Employees”) ‘input data
rs.MoveFirst
‘go to the first row of the record set
EmployeeID = rs.fields(“EmployeeID”) .value
Salary = rs.fields(“Salary”) .value
NewSalary = Salary * 1.10
Response.Write(EmployeeID & “ “ & NewSalary)
‘output results into web page
20
Program Flow
• It is the sequence in which program instructions are
executed, also known as the program
• Program lines are generally executed one at a time in
the order that they are written
• But some instructions can change the flow (i.e., sequence)
• Unconditional branching: changing the program flow
without a specified reason
 e.g., GoTo 100 (go to instruction line #100)
 Except for special cases, unconditional branching is a BAD idea
• Conditional branching: changing the program flow
when certain conditions are met (much more common)
 e.g., If Salary > 100000 then … go to some part of the program
• The various instructions and branching conditions in a
program is know as the program’s “logic”
21
IF, ELSE, ENDIF
(VB.NET)
• IF structures are one of the most popular (conditional branching)
programming concepts. e.g.:
if Salary < 100000 then ‘you can enter comments like this
NewSalary = Salary * 1.15 ‘it is customary to indent for readability
else ‘this is optional
NewSalary = Salary * 1.10
end if ‘an if statement MUST be coupled with an end if
• Nested IF’s:
if Salary < 100000 then ‘common error: forgetting then
if YearsOfService > 10 THEN
NewSalary = Salary * 1.20
else
NewSalary = Salary * 1.15
end if ‘common error: not spacing end if
else
NewSalary = Salary * 1.10
end if
22
IF, ELSE
(JavaScript)
• The IF examples from the prior slide would have to be written differently in
JavaScript
// You can enter comments like this – notice the if block with ( ), { } and ;
// Common mistakes: misplacing { }; forgetting the ;
if (Salary < 100000) {NewSalary = Salary * 1.15;}
else {NewSalary = Salary * 1.10;}
// No need for end if  the } ends the if block
• Nested IF’s:
// Notice that you can place the { } in other lines
// Common mistake: you need one } for each {
if (IF Salary < 100000) {
if (YearsOfService > 10)
{NewSalary = Salary * 1.20;}
else
{NewSalary = Salary * 1.15;}
}
else {NewSalary = Salary * 1.10;}
23
Loops
(ASP.NET and VB.NET)
• Loops are very useful when you want to perform similar calculations a
number of times until a certain condition is met.
Example – For/Next Loop
NumEmployees = 10 ‘good practice to group key variables together
TotPayroll = 0 ‘common practice to keep an accumulator or count variable
for i = 1 to NumEmployees
TotPayroll = TotPayroll + Salary(i) ‘an array that contains salary amounts
next ‘automatically increases i by 1
‘ You could have for i = 1 to 10 step 2 above to increase by 2 in each loop
Example – Do While Loop
rs = Execute(“SELECT EmpID, Salary, NewSalary FROM Employees”)
rs.MoveFirst ‘Start with the first record of the record set rs
x=1
do while not rs.eof ‘eof means end of file or last record of rs
NewSalary(x) = Salary(x) * 1.10
x = x +1 ‘do while doesn’t keep a counter, you must keep it yourself
rs.MoveNext ‘advance to the next record in rs
loop ‘common mistake: every do while needs a loop somewhere else
24
Loops
(JavaScript)
Example – For/Next Loop
var NumEmployees = 10;
var TotPayroll = 0;
for (i = 1; i<=NumEmployees; i++) {
// i++ increases i by 1 in each loop; i = i + 2 would increment by 2
// i– – would decrease i by 1 in each loop
TotPayroll = TotPayroll + Salary(i);
} ‘no need for next – the } keeps the for block together
Example – Do While Loop
var i = 0;
do {
document.write("<p> The value of i is ” + i + "</p>");
i+=2; } /increment i by 2
while(i<=20); /stop after i exceeds 20
25
Functions
(VB.NET)
• Built-in – every software language has built in functions, examples:
 now() gives today’s date and time
 Sum(2,3,5) – adds 2+3+5
 DateSerial(2001,2,1) – converts date to 2/1/2001 format
• Defined – you need to create them – see age function below
 Functions are created (programmed) first and then invoked
 Functions often include parameters, but they don’t have to
 Functions often return a result, but they don’t have to
VB.NET Example:
First define the function:
function age(BirthDate)
DaysSinceBirth = now() – BirthDate
age = int(DaysSinceBirth/365)
end function
Parameter
No Parameter
Value returned
Then invoke the function as needed with something like:
MyAge = age(DateSerial(1990,2,4))
26
Functions
(JavaScript)
JavaScript Example
function squareMe(x)
{
var MySquare = x*x;
return MySquare;
}
Somewhere else in the program you can use something like:
var i;
for(i=1; i<=5; i++)
{
document.write(“<p>The square of " + i + " is " + squareMe(i));
}
27
Example: Counting Chocolates
Var color()
Var flavor()
TotChocolates()
(in Structured English)
‘declare a chocolate color variable array
‘declare a chocolate flavor variable array
‘declare a chocolate counter variable array
color[1] = “red”; color[2] = “blue”; color[3] = “orange”
flavor[1] = “dark”; flavor[2] = “milk”; flavor[3] = “caramel”
‘assign colors
‘assign flavors
TotChocolates[1] = TotChocolates[2] = TotChocolates[3] = 0
GrandTotal = 0
‘set student counter to 0
NumStudents = 0
‘set student counter to 0
Var StudentName()
‘declare a student name variable array
‘set chocolate counters to 0
For n = 1 to Last Student
‘loop through each student
StudentName[n] = Input StudentName
‘Get student name variable array
NumStudents = NumStudents + 1
‘Count student
TotChocolates[1] = TotChocolates[1] + Input “Number of red chocolates?”
TotChocolates[2] = TotChocolates[2] + Input “Number of blue chocolates?”
TotChocolates[3] = TotChocolates[3] + Input “Number of orange chocolates?”
GrandTotal = GrandTotal + TotChocolates[1] + TotChocolates[2] + TotChocolates[3]
Next n
‘next student
For i = 1 to 3
‘display counting results by color
Output “Total Number of ” + color[i] + “chocolates “ + of flavor “ + flavor[i] + = “ + TotChocolates[i]
Next I
Output “Total Number of chocolates = “ + GrandTotal
‘display grand total
28
Exercise for
Lab JS2 – For Loops and
Lab JS2 – IF’s
29
Exercise 1:
Car Loan Payments
You get a 3-year, $10,000 car loan from the bank
at a 3% annual interest. How much are your
monthly payments?
30
Exercise
(The math behind the solution)
First, let’s understand the mathematics behind the required calculation:
Payments are made monthly, not yearly, so we need to figure out the
number of payment periods and the compounding interest per period (i.e.,
per month).
L = $10,000
n = Months = 12 * Years = 12 * 3 = 36
i = Monthly Interest = Annual Interest / 12 = 0.03 / 12 = 0.0025
Monthly Payment = L * i *
(1 + (1 + i) 1n - 1 )
Monthly Payment = 10000 * 0.0025 *
(1 +
1
(1 + 0.0025) 36 - 1
) = 290.81
31
Exercise
(Excel Solution)
32
Exercise
(The JavaScript Program for 3 yrs only)
// Declare and initialize variables
var LoanAmount = 10000;
var annualRate = 0.03;
// The percent below is only to display 0.03 as 3% - not needed to calculate
var annualPercent = annualRate*100;
// Compute the monthly interest rate and total number of (monthly) payments
var monthlyRate = annualRate/12;
var months = 12*yrs;
// Now a tough one, apply the monthly payment formula
// Notes: In JavaScript Math.Pow(x,n) calculates xn
//
See how I use parentheses to ensure the proper computation sequence
//
You can break a single instruction into multiple lines 
//
the command continues until it finds the ;
var monthlyPayment =
LoanAmount * monthlyRate *
(1 + 1 / ( (Math.pow( (1+monthlyRate), months) ) - 1) );
// The toFixed(n) is a JavaScript method to format to n decimals
monthlyPayment = monthlyPayment.toFixed(2);
33
Exercise
(Expressions)
// Let’s look more closely at the expression:
LoanAmount * monthlyRate *
(1 + 1 / ( (Math.pow( (1+monthlyRate), months) ) - 1) );
// Expressions evaluate in this general order: (1) inner parenthesis; (2) outer
// parenthesis; (3) power operations; (4) multiplications and divisions;
// (5) additions and subtractions; and (6) when equal, left to right
LoanAmount * monthlyRate *
(1 + 1 / ( (Math.pow( (1+monthlyRate), months) ) - 1) );
1st  1+i
2nd  {(1+i), n}
rd  (1+i)n
2
3nd
4th  (1+i)n -1
5th  1+
1
(1+i)n -1
34
Exercise for
HW3 – Counting Bills
35
Exercise 2: Counting Bills
You need to pay a payroll for several workers in
cash. You have each individual salary amount in
a database and you need to bring to the job site
an “exact” amount of cash to pay everyone
without having to receive change.
Write a program that will read all salaries from a
database and then compute the total number of
20, 10, 5 and 1 dollar bills you need to get from
the bank to pay everyone their exact salary.
36
Excel Solution
37
Structured English Solution
– 1 Employee Only)
SalaryPmt = 1,239
B20 = Integer(SalaryPmt/20) ‘# $20 bills
Remainder = SalaryPmt – 20*B20
B10 = Integer(Reminder/10) ‘# $10 bills
Remainder = Reminder – 10*B10
B5 = Integer(Reminder/5) ‘# $5 bills
B1 = Reminder – 5*B5 ‘# $1 bills
Output B20, B10, B5, B1
38
Exercise
(Structured English Solution)
NumEmployees = 10
‘change this value for more or less employees
Var SalaryPmt()
‘declare variable as an array
Payroll = 0
‘create a variable to accumulate salary payments
B20 = B10 = B5 = B1 = 0 ‘counters for number of bills
For i = 1 to NumEmployees ‘loop through each employee
Input SalaryPmt[i]
Payroll = Payroll + SalaryPmt [i]
B20 = B20 + Integer(SalaryPmt [i]/20)
Remainder = SalaryPmt [i] – 20*B20
B10 = B10 + Integer(Reminder/10)
Remainder = Reminder – 10*B10
B5 = B5 + Integer(Reminder/5)
B1 = Reminder – 5*B5
Next i
Output Payroll, B20, B10, B5, B1
39