Command

Command: package a request as an object

Problem: you want to store, queue, log, or undo an action — which means the action must be a thing, not just a method call.

PawWalk scenario: background jobs. Each job IS a command: an object responding to call. A runner executes a list of them in order.

In Ruby, 'responds to call' is the whole contract — an object with a call method, a lambda, or a Proc all qualify.