object oriented programming systems
Post on 15-May-2015
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Object Oriented Programming Systems
An Overview
Object Oriented Analysis And Design
•Software development process consists of analysis, design, and implementation phases
•The goal of the analysis phase is a complete description of what the software product should do
•The goal of object-oriented design is the identification of classes, their responsibilities, and the relationships among them
•The goal of the implementation phase is the programming, testing, and deployment of the software product
Why OOPS ?
• To modularize software development , just like any other engineering discipline
•To make software projects more manageable and predictable
•For better maintainability, since software maintenance costs were more than the development costs.
•For more reuse of code and to prevent the ‘reinvention of the wheel’ every time
Programming Techniques
Unstructured Programming
Structured Programming
Modular Programming
Object-Oriented Programming
Modeling
Use Cases
A use case lists a sequence of actions that yields a result that is of value to an actor
Abstract Data Type
OOPS
• A class specifies objects with the same behavior
•An instance of a class is an object that belongs to the given class
•Class names should be nouns in the singular form
•To discover responsibilities , look for verbs in the problem description.
•A responsibility must belong to exactly one class
An OO Program
A circle is a point and a radius
Class and Object concept
An object is characterized by its state, behavior, and identity
• The collection of all information held by an object is its state
•The behavior of an object is defined by the operations or methods that an object supports
•The unique reference (or name) of an object is its identity
An object of circle is a kind of point
If Logo is circle and triangle
Has-A relationship
Relationships between Classes
Three relationships are common among classes :
•Dependency (“uses”)
•Aggregation (“has”)
•Inheritance (“is”)
Dependency
• A class depends on another class if it manipulates objects of the other class in any way.
•If a class can carry out all its tasks without being aware that the other class even exists, then it doesn’t use that class.
•For example, if there is a Message class which uses the System.Print class, then the Message class is dependant , or coupled with the System.Print class
Aggregation
•A class aggregates another if its objects contain objects of the other class
•Aggregation is often informally described as the ‘has-a’ relationship
Inheritance
A class inherits from another if it incorporates the behavior of the other class
Inheritance
Inheritance
Inheritance tree
ASP.NET component
using System;using System.Web.UI;
namespace MSPress.ServerControls {
public class SimpleControl : Control {
protected override void Render(HtmlTextWriter writer){
writer.Write("I don't do anything useful. ");writer.Write("but at least i'm a control....");
}
}
}
Re-using the component
<%@ Page language="C#" %>
<%@ Register TagPrefix="msp" NameSpace="MSPress.ServerControls" Assembly="SimpleControl.cs" %>
<HTML>
<body>
<br>
Here is the output from our first custom control
<br>
<msp:SimpleControl id="simple1" runat="server" />
<br>
</body>
</HTML>
CRC Cards
A CRC card is an index card that describes a class, its high-level responsibilities , and its collaborators
Polymorphism
Sample Program – Part 1using System;
public class Control
{
public Control (string data) {Data = data; }
protected string data;
public string Data
{
get { return data ; }
set { data = value; }
}
}
Sample Program – Part 2
interface IValidate
{
bool Validate();
}
class SSN : Control, IValidate
{// Class starts here
const char DELIMITER = '-';
Sample Program – Part 3
public SSN(string val) : base (val) {}
public bool Validate()
{
Console.WriteLine("[SSN.Validate] : Validating '{0}'", data);
return (11 == data.Length) && (CorrectFormat());
}
Sample Program – Part 4
protected bool CorrectFormat()
{bool correctFormat = true;
for (int i = 0; (correctFormat && i < data.Length); i++)
{
correctFormat =((IsDelimiterPosition(i) && data[i] == DELIMITER)|| (IsNumberPosition(i)&& char.IsNumber(data[i])));
}
return correctFormat; }
Sample Program – Part 5protected bool IsDelimiterPosition(int i)
{
return (i==3 | i==6);
}
protected bool IsNumberPosition (int i)
{
return (i !=3 && i != 6);
}
} //class SSN : Control, IValidate ends here
Sample Program – Part 6
class InterfacesApp
{ //Main class starts here
public static void Main(string[] args)
{
string data = "";
if (0 < args.GetLength(0))
data = args[0];
SSN ssn = new SSN(data);
IValidate val = (IValidate)ssn;
Sample Program – Part 7
Console.WriteLine("[Main] Calling SSN.Validate");
bool success = val.Validate();
Console.WriteLine("[Main] The validation of " +
"SSN '{0}' was {1}successful",
ssn.Data,
(true == success ? "" : "NOT "));
}
} //Main class ends here
COM
Messages
.NET
.NET has 5 intrinsic types :
•Class
•Interface
•Struct
•Enum
•Delegate
A simple example of .NET delegate – Part 1
' Our delegate type can point to any method
' taking two integers and returning an integer.
Public Delegate Function BinaryOp(ByVal x As Integer, ByVal y As Integer) As Integer
A simple example of .NET delegate – Part 2
'This class defines the methods that will be 'pointed to' by the delegate.
Public Class SimpleMath
Public Shared Function Add(ByVal x As Integer, ByVal y As Integer) As Integer
Return x + y
End Function
Public Shared Function Subtract(ByVal x As Integer, ByVal y As Integer) As Integer
Return x - y
End Function
End Class
A simple example of .NET delegate – Part 3
Module Program
Sub Main()
Console.WriteLine("****** Simple Delegate Example*******")
'Make a delegate object and add method to invocation
'list using the AddressOf keyword.
Dim b As BinaryOp = New BinaryOp(AddressOf SimpleMath.Add)
'Invoke the method 'pointed to'
Console.WriteLine("10 + 10 is {0}", b(10, 10))
Console.ReadLine()
End Sub
End Module
The Move from Two-Tier to N-Tier Architecture
Stored Procedures for Business Logic
Two Tier can be messy
Introducing middle tier
The ‘abilities’
Maintainability
Usability
Reliability
Scalability
Security
Integrity
Testability
Performance
Summary
Object Oriented systems are a way of engineering software applications to achieve more consistency and maintainability .
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