FACTORY METHOD / PRACTICE

Start a round.
Let its question vary.

You followed a vehicle from its creation hook back into dispatch(). Now build the same kind of boundary for quiz questions.

YOUR BRIEF

New question types, one round workflow.

The framework starts a round, obtains a question, calls ask(), and packages the prompt with a common heading and ten-point score. Math and science rounds need different question objects.

Assemble a creation hook that lets each concrete round supply its question. Predict the next call and trace both rounds before extending the quiz with a word round.

Shared workflow: dispatch() → QuizRound.start()
Creation hook: createTransport() → createQuestion()
Concrete creator: RoadDelivery → MathRound
Created product: Truck → MathQuestion

The product contract

interface Question { ask(): string }

Keep the common workflow in the creator. Each subclass overrides creation; it does not copy the entire workflow.

01 / ASSEMBLE

Give the workflow a creation hook.

Choose a product contract, a shared workflow and which concrete round setup selects.

What does the creation method return?How does the shared workflow obtain a question?Which creator should setup select?

Inspect your full assembled code

Your assembled code

TypeScript preview. Highlighting follows the selected execution. The plain-string choice deliberately fails this workflow's ask() contract. In the branching version, creator subclasses are unused.

1. Products and card

// Choose a product contract.

2. Shared workflow

// Choose how the shared workflow gets a question.

3. Concrete creators

// Choose which concrete creator setup selects.

4. Setup and result

// Complete the workflow and creator pieces to wire a round.

02 / PREDICT & TRACE

Follow the question back to its creator.

Start a trace, predict the call at the creation boundary, then follow the object back into the workflow. Each step waits for you.

Test case

Choose all three pieces in step 1 to unlock the creation trace.

Expected prompt: What is 2 + 3?

Who creates the question?

Your trace will show the selected workflow, creation decision and resulting object together. Assemble the pieces above, then start.

○ Math round — finish a passing trace to verify
○ Science round — finish a passing trace to verify

This replays a local run of your selected assembly. Excerpts omit recording callbacks.

03 / TRANSFER THE IDEA

A word round joins the quiz.

It asks “What is the opposite of quiet?” and uses the same heading and ten-point score. Which edits add this round while preserving the shared workflow?

First finish passing Math and Science traces with the same assembly.

Select all required editsAdd WordQuestion implementing Question.Add WordRound overriding createQuestion().Let setup select WordRound.Add a word branch inside QuizRound.start().Teach MathQuestion about word questions.

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