![Class Attributes
• attributes (fields, instance variables)
▫ visibility name : type [count] =
default_value
▫ visibility: + public
# protected
- private
~ package (default)
/ derived
▫ underline static attributes
▫ derived attribute: not stored, but can be
computed from other attribute values
▫ attribute example:
balance : - = double 0.00
7](https://image.slidesharecdn.com/ooadlec16-classdiagram-210303092104/85/Ooad-class-diagram-7-320.jpg)
Ooad( class diagram)
- 1. Object Oriented Analysis & Design Lecture 16 Class Diagrams Sajiya Tariq
- 2. Overview •The class diagram is a static diagram. It represents the static view of an application. •The class diagram describes the attributes and operations of a class and also the constraints imposed on the system. •The only UML diagrams which can be mapped directly with object oriented languages. •The class diagram shows a collection of classes, interfaces, associations, collaborations and constraints. It is also known as a structural diagram. 2
- 3. Purpose The purpose of the class diagram can be summarized as: •Analysis and design of the static view of an application. •Describe responsibilities of a system. •Base for component and deployment diagrams. •Forward and reverse engineering. 3
- 4. Points to remember • The name of the class diagram should be meaningful to describe the aspect of the system. • Each element and their relationships should be identified in advance. • Responsibility (attributes and methods) of each class should be clearly identified. • For each class minimum number of properties should be specified. Because unnecessary properties will make the diagram complicated. • Use notes when ever required to describe some aspect of the diagram. Because at the end of the drawing it should be understandable to the developer/coder. • Finally, before making the final version, the diagram should be drawn on plain paper and rework as many times as possible to make it correct. 4
- 5. UML Class Diagram • What is a UML class diagram? ▫ UML class diagram: a picture of ▫ the classes in an OO system ▫ their fields and methods ▫ connections between the classes that interact or inherit from each other • What are some things that are not represented in a UML class diagram? ▫ details of how the classes interact with each other ▫ algorithmic details; how a particular behavior is ▫ implemented 5
- 6. Diagram of one Class • class name in top of box ▫ write <<interface>> on top of interfaces' names ▫ use italics for an abstract class name • Attributes (optional) ▫ should include all fields of the object • Operations / methods (optional) ▫ may omit trivial (get/set) methods but don't omit any methods from an interface! ▫ should not include inherited methods 6
- 7. Class Attributes • attributes (fields, instance variables) ▫ visibility name : type [count] = default_value ▫ visibility: + public # protected - private ~ package (default) / derived ▫ underline static attributes ▫ derived attribute: not stored, but can be computed from other attribute values ▫ attribute example: balance : - = double 0.00 7
- 8. Class Operations and Methods 8
- 9. Comments • represented as a folded note, attached to the appropriate class/method/etc by a dashed line 9
- 10. Relationships btwn. classes •generalization: an inheritance relationship ▫inheritance between classes ▫interface implementation •association: a usage relationship ▫dependency ▫aggregation ▫composition 10
- 14. Association types • aggregation: "is part of" ▫ symbolized by a clear white diamond • composition: "is entirely made of" ▫ stronger version of aggregation ▫ the parts live and die with the whole ▫ symbolized by a black diamond • dependency: "uses temporarily" ▫ symbolized by dotted line ▫ often is an implementation detail, not an intrinsic part of that object's state 14