Low-level design

SOLID principles

The five laws of OO design. 5 lessons where the diagrams draw themselves, one class and one message at a time, with the theory and the code beside them.

  • 5 lessons
  • Animated diagrams
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SOLID principles

  1. 1Single Responsibility (S)
  2. 2Open / Closed (O)
  3. 3Liskov Substitution (L)
  4. 4Interface Segregation (I)
  5. 5Dependency Inversion (D)
5 lessons, each with diagrams that draw themselves.

In this module

  • A class should have ONE reason to change. Bundle one responsibility per class; split it the moment a class starts juggling many.
  • Software should be OPEN for extension but CLOSED for modification, add new behaviour by adding code, not by editing code that already works.
  • A subclass must be usable ANYWHERE its parent is, without surprising the caller. If substituting it breaks behaviour, the inheritance is a lie.
  • No client should be forced to depend on methods it doesn’t use. Prefer many small, role-specific interfaces over one fat one.
  • High-level policy shouldn’t depend on low-level details. Point BOTH at an abstraction, and watch the dependency arrow flip.

More low-level design

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DSA comes with the all labs plan and every ChaiCode batch.