Objects, state and responsibility

≈ 42 min

Objects, state and responsibility

Object-oriented programming models a domain using classes. A class defines useful state and behaviour; each object has its own state. Encapsulation keeps a class responsible for protecting the rules that make that state valid.

Reasoning routine. State the information available, the rule to apply, the result required and one boundary or failure case.

Worked example. A Book object stores its title and loan state. Two copies of the same novel are two objects because one can be available while the other is borrowed.

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Which statement best reflects this lesson's encapsulation?

A class defines a structure while an object is one instance with its own state.

Use a vague rule and trust the first result.

Ignore boundary cases and hidden assumptions.

Choose a tool before stating the problem.

Write the key term for this lesson: encapsulation.

A school system needs a reliable next step. Which choice is most defensible for this topic?

Let the object that owns a rule validate the state change before updating it.

Store an unexplained guess and call it evidence.

Give every account unrestricted access.

Hide the error so the report looks complete.

A learner can repeat a definition from Objects, state and responsibility. Which next task gives stronger evidence of mastery?

Apply the idea to an unfamiliar boundary, error or decision and justify the choice.

Repeat the lesson title without using the concept.

Choose the first option before reading the scenario.

Hide an unexpected result so the answer appears tidy.