Assertions, Preconditions, Postconditions and invariants are our allies to avoid invalid objects. Avoiding them leads to hard-to-find errors.
- Contract breaking
- Hard to debug
- Bad cohesion
- Create strong preconditions
- Raise exceptions
- Fail Fast
- Defensive Programming
Constructors are an excellent first line of defense
Anemic Objects lack these rules.
- It's difficult to find missing preconditions, as long with assertions and invariants.
Always be explicit on object integrity.
Turn on production assertions.
Even if it brings performance penalties.
Data and object corruption is harder to find.
Fail fast is a blessing.
Writing a class without its contract would be similar to producing an engineering component (electrical circuit, VLSI (Very Large Scale Integration) chip, bridge, engine...) without a spec. No professional engineer would even consider the idea.