Forms, payloads, and live inputs in Fitz LiveViews

TL;DR — Events in Fitz LiveViews carry data three ways: a click payload ( data-flv-value-* ) tags a button with the value it should send; a form submit ( data-flv-submit ) reads the form's named inputs; and a live value ( @input / @change ) delivers a control's current value in payload["value"] . All three land in the same place — a payload map your handler reads. This post builds a live name list (add / remove / count) that runs both server-rendered and as WebAssembly. (Part 3 of the FitzLiveViews series.) Parts 1 and 2 covered the pitch and the counter. A counter only reads +1 / -1 — no data flows in . Real UIs take input: text, selections, form fields. Here's how that data reaches your handlers. The payload Every event handler has a payload in scope — a Map<Str, Str> . The three mechanisms below all fill it; your handler reads it with payload["key"] (guard with payload.has("key") ): 1. Click payload — a button that carries a value Tag any element with data-flv-value-<key>="{expr}" , and when a data-flv-click on it (or an ancestor) fires, that value rides along: <button data-flv-click= "remove" data-flv-value-item= "{it}" > × </button> event remove () { if ( payload . has ( " item " )) { let target = payload [ " item " ] names = names . filter ( fn ( it ) => it != target ) } } The delete button knows which row it is because the row's value is stamped on it. No IDs threaded through a callback, no closure capture. 2. Form submit — the whole form at once data-flv-submit="handler" on a <form> reads each named input into the payload on submit; data-flv-clear resets a field afterward: <form data-flv-submit= "add" > <input name= "item" placeholder= "Add a name" data-flv-clear /> <button type= "submit" > Add </button> </form> event add () { if ( payload . has ( " item " )) { let n = payload [ " item " ] if ( n != "" ) { names . push ( n ) } } } payload["item"] is the input's value at submit time. No preventDefault , no FormData , no fetch . 3. Live value — @input / @chang