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Object-Oriented Programming (OOP) Lecture No. 5

Object-Oriented Programming (OOP) Lecture No. 5. Multiple Inheritance. We may want to reuse characteristics of more than one parent class. Example – Multiple Inheritance. Mermaid. Example – Multiple Inheritance. Woman. Fish. Mermaid. Example – Multiple Inheritance. Amphibious Vehicle.

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Object-Oriented Programming (OOP) Lecture No. 5

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  1. Object-Oriented Programming (OOP)Lecture No. 5 Downloaded From: www.bsit.zxq.net

  2. Multiple Inheritance • We may want to reuse characteristics of more than one parent class Downloaded From: www.bsit.zxq.net

  3. Example – Multiple Inheritance Mermaid Downloaded From: www.bsit.zxq.net

  4. Example – Multiple Inheritance Woman Fish Mermaid Downloaded From: www.bsit.zxq.net

  5. Example – Multiple Inheritance Amphibious Vehicle Downloaded From: www.bsit.zxq.net

  6. Example – Multiple Inheritance Vehicle Land Vehicle Water Vehicle Car Amphibious Vehicle Boat Downloaded From: www.bsit.zxq.net

  7. Problems with Multiple Inheritance • Increased complexity • Reduced understanding • Duplicate features Downloaded From: www.bsit.zxq.net

  8. Problem – Duplicate Features • Which eat operation Mermaid inherits? Woman Fish eat … eat … Mermaid Downloaded From: www.bsit.zxq.net

  9. Solution – Override the Common Feature Woman Fish eat … eat … Mermaid Invoke eat operation of desired class eat … Downloaded From: www.bsit.zxq.net

  10. Problem – Duplicate Features (Diamond Problem) Vehicle • Which changeGear operation Amphibious Vehicle inherits? changeGear Land Vehicle Water Vehicle Car Amphibious Vehicle Boat Downloaded From: www.bsit.zxq.net

  11. Solution to Diamond Problem • Some languages disallow diamond hierarchy • Others provide mechanism to ignore characteristics from one side Downloaded From: www.bsit.zxq.net

  12. Association • Objects in an object model interact with each other • Usually an object provides services to several other objects • An object keeps associations with other objects to delegate tasks Downloaded From: www.bsit.zxq.net

  13. Kinds of Association • Class Association • Inheritance • Object Association • Simple Association • Composition • Aggregation Downloaded From: www.bsit.zxq.net

  14. Simple Association • Is the weakest link between objects • Is a reference by which one object can interact with some other object • Is simply called as “association” Downloaded From: www.bsit.zxq.net

  15. Kinds of Simple Association • w.r.t navigation • One-way Association • Two-way Association • w.r.t number of objects • Binary Association • Ternary Association • N-ary Association Downloaded From: www.bsit.zxq.net

  16. One-way Association • We can navigate along a single direction only • Denoted by an arrow towards the server object Downloaded From: www.bsit.zxq.net

  17. Example – Association • Ali lives in a House Ali lives-in House 1 1 Downloaded From: www.bsit.zxq.net

  18. Example – Association • Ali drives his Car Ali drives Car 1 * Downloaded From: www.bsit.zxq.net

  19. Two-way Association • We can navigate in both directions • Denoted by a line between the associated objects Downloaded From: www.bsit.zxq.net

  20. Example – Two-way Association • Employee works for company • Company employs employees Employee works-for Company * 1 Downloaded From: www.bsit.zxq.net

  21. Example – Two-way Association • Yasir is a friend of Ali • Ali is a friend of Yasir Yasir friend Ali 1 1 Downloaded From: www.bsit.zxq.net

  22. Binary Association • Associates objects of exactly two classes • Denoted by a line, or an arrow between the associated objects Downloaded From: www.bsit.zxq.net

  23. Example – Binary Association • Association “works-for” associates objects of exactly two classes Employee works-for Company * 1 Downloaded From: www.bsit.zxq.net

  24. Example – Binary Association • Association “drives” associates objects of exactly two classes Ali drives Car 1 * Downloaded From: www.bsit.zxq.net

  25. Ternary Association • Associates objects of exactly three classes • Denoted by a diamond with lines connected to associated objects Downloaded From: www.bsit.zxq.net

  26. Example – Ternary Association • Objects of exactly three classes are associated Student Teacher 1 * * Course Downloaded From: www.bsit.zxq.net

  27. Example – Ternary Association • Objects of exactly three classes are associated Project Language * * 1 Person Downloaded From: www.bsit.zxq.net

  28. N-ary Association • An association between 3 or more classes • Practical examples are very rare Downloaded From: www.bsit.zxq.net

  29. Composition • An object may be composed of other smaller objects • The relationship between the “part” objects and the “whole” object is known as Composition • Composition is represented by a line with a filled-diamond head towards the composer object Downloaded From: www.bsit.zxq.net

  30. Example – Composition of Ali Head 1 Arm Leg Ali 2 2 1 Body Downloaded From: www.bsit.zxq.net

  31. Example – Composition of Chair Back 1 Chair 1 2 4 Arm Seat Leg Downloaded From: www.bsit.zxq.net

  32. Composition is Stronger • Composition is a stronger relationship, because • Composed object becomes a part of the composer • Composed object can’t exist independently Downloaded From: www.bsit.zxq.net

  33. Example – Composition is Stronger • Ali is made up of different body parts • They can’t exist independent of Ali Downloaded From: www.bsit.zxq.net

  34. Example – Composition is Stronger • Chair’s body is made up of different parts • They can’t exist independently Downloaded From: www.bsit.zxq.net

  35. Aggregation • An object may contain a collection (aggregate) of other objects • The relationship between the container and the contained object is called aggregation • Aggregation is represented by a line with unfilled-diamond head towards the container Downloaded From: www.bsit.zxq.net

  36. Example – Aggregation Bed 1 Chair Room Table * 1 1 Cupboard Downloaded From: www.bsit.zxq.net

  37. Example – Aggregation Garden Plant * Downloaded From: www.bsit.zxq.net

  38. Aggregation is Weaker • Aggregation is weaker relationship, because • Aggregate object is not a part of the container • Aggregate object can exist independently Downloaded From: www.bsit.zxq.net

  39. Example – Aggregation is Weaker • Furniture is not an intrinsic part of room • Furniture can be shifted to another room, and so can exist independent of a particular room Downloaded From: www.bsit.zxq.net

  40. Example – Aggregation is Weaker • A plant is not an intrinsic part of a garden • It can be planted in some other garden, and so can exist independent of a particular garden Downloaded From: www.bsit.zxq.net

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