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B3.2 Fundamentals of OOP for multiple classesB3.2.4

Composition and Aggregation in Class Relationships

Explain the role of composition and aggregation in class relationships

AHL≈ 50 minCommand term: ExplainPremium

In this lesson

  • Designing objects from smaller component objects (“has a” relationships)
  • Distinguishing aggregation, where the parts exist independently, from composition, where they cannot
  • Recognising both relationships in code and in UML class diagrams
  • Choosing between inheritance, aggregation and composition

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What's inside

  1. LearnBuilt from parts
  2. LabWhat survives?
  3. CodeComposition in code
  4. CodeAggregation in code
  5. LearnAggregation and composition in UML
  6. LearnComparing the relationships
  7. CheckAggregation or composition?
  8. CheckQuick check
  9. ExamWorked exam answer
  10. ReviewMistakes examiners see
  11. Exam practiceExam-style questions

Ends with 3 exam-style questions worth 9 marks, with a self-marking markscheme.