Factory & Creational

Mental model

Creational patterns (Factory, Builder, Singleton) hide how an object is constructed so callers do not pin themselves to a specific concrete class. They earn their keep when you add the 4th variant without callers needing to change.

How to study Factory & Creational

Begin by restating the mental model in your own words, then connect it to a concrete system you have built or operated. Name the mechanism, the constraint it addresses, and the trade-off it introduces. Use Refactoring Guru — Factory Method to check details, but close the source before writing your explanation. Retrieval is the learning step; rereading is only preparation.

Next, compare Factory & Creational with the neighboring concepts in its roadmap. Ask what changes in correctness, latency, resource use, operability, and failure recovery. Complete Notification factory and preserve the command, input, output, and one failed attempt as evidence. Finish by explaining the idea without jargon to someone who has not studied the track.

Proof of understanding

• Explain the mechanism from first principles and identify the state it reads or changes.
• Give one situation where the concept is the right choice and one where it is not.
• Predict a realistic failure mode before running the drill, then compare the prediction with evidence.
• Connect the result to a roadmap or build artifact instead of treating the concept as isolated trivia.

Learn from primary sources

• Refactoring Guru — Factory Method (doc)

Practice and explain it back

Review prompts

• What is the concrete signal that a factory earns its keep rather than just adding a layer?

Build evidence

Use a roadmap capstone to turn this concept into working evidence.

Learning paths

• LLD Practice