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Combine is Apple's framework for handling values that arrive over time, like taps, timers, or network responses. 🌊

Instead of asking for data once, you describe a stream of values and react each time a new one arrives, now or later.

A Publisher is the source. It emits values downstream and tells you when it finishes or fails.

Every publisher declares two types: its Output (the values it sends) and its Failure (the error it may throw).

A Subscriber attaches to a publisher, receives each value as it arrives, and decides what to do with it.

The sink subscriber is the simplest one: you hand it a closure that runs for every value received.

A fuller sink takes two closures: one for completion (finished or failure) and one for each value.

Subscribing returns a cancellable. Keep it alive, or the stream is torn down immediately.

Just emits one value then finishes. Empty finishes with no values at all. Both are handy building blocks.

A PassthroughSubject lets you send values manually, perfect for forwarding events you control.

The subscriber signals demand, the publisher pushes values, and completion ends the relationship cleanly.

You met the three players: a publisher emits values, a subscriber receives them, and a stored cancellable keeps the link alive. 🎉