Object-Oriented Concepts in AB Suite

Июль 31, 2022

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Object-Oriented Concepts in AB Suite

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2. Objective By the end of this module, you’ll be able to— Define object-oriented concepts Implement object-oriented
3. Module Topics Object-Oriented Concepts—An Overview History of object-orientation Objects Classes Instances Methods Principles of Object-Orientation Encapsulation
4. Object-Oriented Concepts—An Overview
5. History of Object-Orientation Object-Orientation (OO): Developed at Xerox’s Palo Alto Research Center in the 1970s Developed
6. Some Key Object Oriented Principles
7. Objects An object is the UML way of representing an entity Real, like a car Conceptual,
8. AB Suite Objects
9. Classes A class acts as a blueprint of an object. A class describes a group of
10. Class Types Primitive class — Is an abstract description of a simple item of data, such
11. Instances Instances defined by AB Suite objects are: Attribute - Member of an object that holds
12. Current Instance Current Instance is the particular instance of an object being invoked. Current instance qualifiers
13. Example Consider that the CUST ispec contains a user defined method MyMethod(). MyMethod() contains logic that
14. Methods Methods contain logic that defines the behavior of a class. Provide an interface to the
15. Parameters and Return Variables Method parameters and return variables return during a method call. Values passed
16. Method Logic Method Logic defines the behavior of a class. It protects the calling method from
17. Principles of Object Orientation
18. Encapsulation Encapsulation is also known as information hiding. It works on the concept of visibility and
19. Example Business Rule: A Product’s Stock balance (STOCKBAL) should never be less than zero Stock balance
20. Encapsulation—Best Practices Convert a single code sequence into smaller pieces of code. This avoids redundancy and
21. Composition Composition is a way of combining existing simple objects to build new and more complex
22. Example 1 CASH and SALE events contain an instance of the CUST ispec Customer Number field
23. Example 2 In System Modeler, a composite class: Can be used anywhere in the model Can
24. Generalization Generalization is the process of factoring out common behavior and structuring them into another class.
25. Inheritance Inheritance is a relationship between two classes. In this mechanism, a class (subclass) inherits attributes,
26. Example Superclass More Generalized Subclass More Specialized
27. Customizing Inherited Behavior Customizing Inherited Behavior is commonly known as overriding members. In this process subclass
28. IsInner Relationship Inner class is defined as a class within another class. Instances of the inner
29. Polymorphism Polymorphism is one of the useful applications of Inheritances. It provides the ability to refer
30. AB Suite Framework
31. AB Suite Framework Objects AB Suite Framework objects consist of built-in: Classes Instances Methods Framework objects
32. Stereotypes Stereotype indicates how an object behaves in the AB Suite framework processing cycle. For example,
33. Overriding Framework Methods Stereotyped classes inherit a set of framework methods that do not contain any
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Objective
By the end of this module, you’ll be able to—
Define object-oriented

concepts
Implement object-oriented concepts in AB Suite application development

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Module Topics
Object-Oriented Concepts—An Overview
History of object-orientation
Objects
Classes
Instances
Methods
Principles of Object-Orientation
Encapsulation
Composition
Generalization
Inheritance
Polymorphism
AB

Suite Framework

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Object-Oriented Concepts—An Overview

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History of Object-Orientation
Object-Orientation (OO):
Developed at Xerox’s Palo Alto Research Center in

the 1970s
Developed to make software development simpler
Developed to simplify applications and improve maintainability

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Some Key Object Oriented Principles

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Objects
An object is the UML way of representing an entity
Real, like

a car
Conceptual, like a bank transaction
An object is a software bundle of related state and behavior
State is the current condition an object is in and it might change
Behavior is how an object responds to operations

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AB Suite Objects

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Classes
A class acts as a blueprint of an object.
A class describes

a group of objects that are the same.
An instance is an individual object of a class at runtime.

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Class Types
Primitive class — Is an abstract description of a simple

item of data, such as a customer name or age. For example, strings, numbers, and so on.
Complex class — Is a composition of other classes.

Belongs to the Customer class, a Complex class

Name: Jenny (String)
Gender: Female (String)
Age: 42 (Number)

Primitive classes

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Instances
Instances defined by AB Suite objects are:
Attribute - Member of an

object that holds the state of a class
Variable - Temporary storage for information
Parameter - Special variable used to pass data into and/or out of a method call
You can define an instance of a class by setting its Multiplicity property to > 0.
For example, to create an instance of class Customer, set the Multiplicity property of the Customer element to 1.

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Current Instance
Current Instance is the particular instance of an object being

invoked.
Current instance qualifiers in System Modeler:
This—Refers to the current instance in which the method is running, this can a framework instance or a user-defined instance
Super—Refers to the superclass of the current instance
Owner—Refers to the owner of the current instance
Component—Refers to the current segment
Current instance qualifiers help to reduce programming logic.

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Example
Consider that the CUST ispec contains a user defined method MyMethod().
MyMethod()

contains logic that refers fields from the CUST table.
Consider an instance of CUST ispec, MyCUST in the SALE event.
When MyMethod() is invoked from MyCUST, the logic is:

Referring the instance using the current instance qualifier

Referring the instance by name

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Methods
Methods contain logic that defines the behavior of a class.
Provide an

interface to the class using:
Parameters
Return variables
AB Suite methods:

Framework Methods

User Defined Method

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Parameters and Return Variables
Method parameters and return variables return during a

method call.
Values passed back to the calling method can prompt the calling method to take a particular action.
You can set the return value of a method using the Return command

Return CUSTOMER

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Method Logic
Method Logic defines the behavior of a class.
It protects the

calling method from internal changes.
You can write method logic using current instances by:
Explicitly specifying the current instance qualifier
Implicitly specifying the attribute name of the instance

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Principles of Object Orientation

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Encapsulation
Encapsulation is also known as information hiding.
It works on the concept

of visibility and ownership of members
It is a means of managing access to an object’s members
Private ( ), visible only within the class
Protected ( ), visible within its class and any class inheriting from it
Public ( ), visible outside the class
It reduces maintenance cost by minimizing scope of change.

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Example
Business Rule: A Product’s Stock balance (STOCKBAL) should never be less

than zero

Stock balance = STOCKBAL – Quantity
(STOCKBAL) 1000 – 1500
= -500

STOCKBAL updated, but STOCKBAL is < 0, which is against business rule

Sale Event

Without Encapsulation

With Encapsulation

Stock balance = STOCKBAL – Quantity
(STOCKBAL)

STOCKBAL is not updated, as STOCKBAL is < 0

Sale Event

UpdateStockbal()

Returns False

STOCKBAL is Public

STOCKBAL is Private

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Encapsulation—Best Practices
Convert a single code sequence into smaller pieces of code.

This avoids redundancy and helps in reuse of code.
Set the class members that represent the object as Private.
Set the class members that service the external needs of other classes (typically methods) as Public.
Hide implementation by setting the members protected or private.
Expose only interfaces by use of public methods.
Use parameters to pass information from one class to another and into or out of methods.
Do not use global variables for encapsulation.
Set variables that are used only within a method as local variables.

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Composition
Composition is a way of combining existing simple objects to build

new and more complex objects.
For example, a Customer object is a composition of Name, Address, Credit limit, and so on
It models a relationship between two objects where one object owns, or is made up of, other objects.
It uses attributes that can have special characteristic such as:
Persistence
Presentation

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Example 1
CASH and SALE events contain an instance of the CUST

ispec

Customer Number field appears as a drop-down list in the CASH event presentation

Customer Number field appears as a drop-down list in the SALE event presentation

CUST ispec presentation

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Example 2
In System Modeler, a composite class:
Can be used anywhere in

the model
Can be used more than once in an class

SalesOrder
orderNum
custID
billAddress
delivAddress

Address
streetNum
streetName
streetType
town

billAddress

delivAddress

SalesOrder object owns two instances of Address class

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Generalization
Generalization is the process of factoring out common behavior and structuring

them into another class.
An inheritance hierarchy is formed between the objects
The generalized object is referred to as the superclass
The specializing object is referred to as the subclass
It promotes reuse, reducing complexity among similar objects.

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Inheritance
Inheritance is a relationship between two classes.
In this mechanism, a class

(subclass) inherits attributes, methods, and relationship of another class (superclass).
It allows the reuse of members of a class, reducing the complexity amongst similar objects.
In System Modeler, the Inherits property enables a “subclass” to acquire all the behavior of its “superclass”.

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Example
Superclass
More
Generalized
Subclass
More
Specialized

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Customizing Inherited Behavior
Customizing Inherited Behavior is commonly known as overriding members.
In

this process subclass members with the same name as the superclass members are overridden.
You cannot override a member if its IsFinal property is set to True.

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IsInner Relationship
Inner class is defined as a class within another class.
Instances

of the inner class have access to the attributes and methods of its owner.
In System Modeler, the inner class behavior is implemented using the IsInnerClass property.
IsInner is a concept that allows classes to interact through the structural ownership relationship.
IsInner relationship is a simplified interface to private members and the cost of weakened encapsulation.

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Polymorphism
Polymorphism is one of the useful applications of Inheritances.
It provides the

ability to refer to the instance of a subclass through a common interface defined in the superclass.
In System Modeler, Inherits property is used to associate the objects that are polymorphic.
Overriding the superclass method enhances the capabilities of polymorphism.

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AB Suite Framework

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AB Suite Framework Objects
AB Suite Framework objects consist of built-in:
Classes
Instances
Methods
Framework objects

are inherited implicitly in every user defined class.
Properties of a class control the level of inheritance.
Members inherited from the framework object depend on the primitive type and stereotype.

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Stereotypes
Stereotype indicates how an object behaves in the AB Suite framework

processing cycle.
For example, ispecs and segments are both classes, but they have different stereotypes.
A stereotyped class or object inherits a set of built-in attributes and methods.
For example, the built-in attributes and methods inherited by a segment class include:
An attribute called GLB.
A built-in method called Startup().

Stereotypes in AB Suite

Segment
Ispec
Report
Frame
Group
Insertable
Event
CopyIspec
CopyEvent
SQL Script
Presentation Interface
Serializable Interface

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Overriding Framework Methods
Stereotyped classes inherit a set of framework methods that

do not contain any logic.
To add logic to framework methods invoked during the runtime cycle, you need to override the methods.

Object-Oriented Concepts in AB Suite

Содержание

ObjectiveBy the end of this module, you’ll be able to—Define object-oriented

Module TopicsObject-Oriented Concepts—An OverviewHistory of object-orientationObjectsClasses InstancesMethods Principles of Object-OrientationEncapsulationCompositionGeneralizationInheritance PolymorphismAB

Object-Oriented Concepts—An Overview

History of Object-OrientationObject-Orientation (OO):Developed at Xerox’s Palo Alto Research Center in

Some Key Object Oriented Principles

ObjectsAn object is the UML way of representing an entityReal, like

AB Suite Objects

ClassesA class acts as a blueprint of an object.A class describes

Class TypesPrimitive class — Is an abstract description of a simple

InstancesInstances defined by AB Suite objects are:Attribute - Member of an

Current InstanceCurrent Instance is the particular instance of an object being

ExampleConsider that the CUST ispec contains a user defined method MyMethod().MyMethod()

MethodsMethods contain logic that defines the behavior of a class.Provide an

Parameters and Return VariablesMethod parameters and return variables return during a

Method LogicMethod Logic defines the behavior of a class.It protects the

Principles of Object Orientation

EncapsulationEncapsulation is also known as information hiding.It works on the concept

ExampleBusiness Rule: A Product’s Stock balance (STOCKBAL) should never be less

Encapsulation—Best PracticesConvert a single code sequence into smaller pieces of code.

CompositionComposition is a way of combining existing simple objects to build

Example 1CASH and SALE events contain an instance of the CUST

Example 2In System Modeler, a composite class:Can be used anywhere in

GeneralizationGeneralization is the process of factoring out common behavior and structuring

InheritanceInheritance is a relationship between two classes.In this mechanism, a class

ExampleSuperclassMoreGeneralizedSubclassMoreSpecialized

Customizing Inherited BehaviorCustomizing Inherited Behavior is commonly known as overriding members.In

IsInner RelationshipInner class is defined as a class within another class.Instances

PolymorphismPolymorphism is one of the useful applications of Inheritances.It provides the