1 · Counter

basics.counter — counter.clj, counter_controller.clj.

The smallest complete component: a render fn and a one-state machine. The README animation walks one click of this very component through the pipeline.

State machine

stateDiagram-v2
  direction LR
  [*] --> displayed : INIT / seed 0
  displayed --> displayed : INCREMENT · DECREMENT · RESET (one action each)

What to look at

• The root element carries :id component-id and :data-signals (ds/ctx->data-signals ctx). The first makes the morph land; the second is the whole persistence story — {:count 2} lives in the browser and comes back with every click.
• Each button is "data-on:click" "@post('/ds/nds/basics.counter/counter1/increment')". The event name in the URL is lower-case; the machine sees :INCREMENT.
• INIT does (update-in ctx [:memory :count] #(or % 0)), not assoc 0: a count already in the store survives a second INIT.
• {:actions f} without :target stays in :displayed.

Try it: click, then reload the page — the count is gone. One-shot components own no server state.

Spec: the first tests block in examples_test.clj (INIT seeds 0, increments accumulate through the store, every button posts to this component's own route).