What is Composition Over Inheritance?
Build behavior by combining small objects instead of stacking deep parent classes.
snap on retry · no tree to rebuild
Composition Over Inheritance favors…
Write it in your own words in the app.
In real work
Composition over inheritance: we replaced a deep subclass tree with small composed helpers for logging and retry.
In the illustration
Wedging a new block into the five-high tower makes every block above it lurch; on the rail beside it a retry module simply clicks on next to logging and nothing else moves.
Refactor the Notification class hierarchy with composition over inheritance in your coding agent: replace the four subclasses with a Notification that takes a Channel and a Formatter, and keep every existing test green.
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