Identify Classes - Object Oriented Programming - Lecture Slides, Slides of Object Oriented Programming

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Object-Oriented Modeling

An Example

Problem Statement

• Develop a graphic editor that can draw different geometric shapes such as line, circle and triangle. User can select, move or rotate a shape. To do so, editor provides user with a menu listing different commands. Individual shapes can be grouped together and can behave as a single shape.

…Identify Classes

Eliminate irrelevant classes

• Editor – Very broad scope
• User – Out of system boundary

…Identify Classes

Add classes by analyzing requirements

• Group – required to behave as a shape
  • “Individual shapes can be grouped together and can behave as a single shape”
• View – editor must have a display area

Object Model – Graphic Editor

Line

Circle

Triangle

Shape Group

View

Menu

Identify Associations

Extract verbs connecting objects

• “Individual shapes can be grouped together” - Group consists of lines, circles, triangles - Group can also consists of other groups (Composition)

… Identify Associations

Verify access paths

• Menu sends message to View

(Simple One-Way Association)

Object Model – Graphic Editor

Line Circle Triangle

View Shape

nn nn^ nn

nn

Menu

Group nn nn^ nn

nn

nn

…Identify Attributes

Extract properties of the object

• From the domain knowledge
• Line
• Color
• Vertices
• Length
• Circle
• Color
• Vertices
• Radius
• Triangle
• Color
• Vertices
• Angle
• Shape
• Color
• Vertices

…Identify Attributes

Extract properties of the object

• From the domain knowledge
• Group
• noOfObjects
• View
• noOfObjects
• selected
• Menu
• Name
• isOpen

Identify Operations

Extract verbs connected with an object

• Develop a graphic editor that can draw different geometric shapes such as line, circle and triangle. User can select, move or rotate a shape. To do so, editor provides user with a menu listing different commands. Individual shapes can be grouped together and can behave as a single shape.

… Identify Operations

Eliminate irrelevant operations

• Develop – out of system boundary
• Behave – have broad semantics

…Identify Operations

Following are selected operations:

• Triangle
  • Draw
  • Select
  • Move
  • Rotate
    • Shape
      • Draw
      • Select
      • Move
      • Rotate

…Identify Operations

Following are selected operations:

• Group
  • Draw
  • Select
  • Move
  • Rotate
    • Menu
      • Open
      • Select
      • Move
      • Rotate