Define reactive bindings between state keys and widgets

Reactive bindings auto-update widgets when state values change. Instead of manually calling update() after every state$set(), declare the relationship once and let rtui handle the rest.

Usage

reactive(...)

Arguments

...

Named arguments defining bindings. Each name is a state key, and each value is one of:

character: Widget id — sets the widget's value to the new state value. E.g. count = "display" updates the "display" widget's value whenever state$set("count", x) is called.
formula: A one-sided formula ~ expr where .x is the new value, .state is the state object, and .app is the running app. E.g. count = ~ update(.app, "display", value = paste("Count:", .x))
function: A function function(value, state, app) for full control. Called whenever the state key changes.
list: A list of any of the above, to bind multiple widgets to the same state key.

Value

A list of class "rtui_reactive" to pass to tui_app() or quick_app().

Examples

if (FALSE) { # \dontrun{
# Simple: state$count auto-updates the "display" widget's value
quick_app(
  layout = vstack(
    digits("0", id = "display"),
    button("+1", id = "inc"),
    id = "root"
  ),
  reactive = reactive(
    count = "display"
  ),
  on_click = list(
    inc = function(event, state) {
      state$set("count", state$get("count", 0L) + 1L)
      state
    }
  )
)

# Formula: transform the value before updating
reactive(
  count = ~ update(.app, "label", content = paste("Count is", .x))
)

# Function: full control
reactive(
  temperature = function(value, state, app) {
    update(app, "temp_display", value = paste0(value, "°C"))
    if (value > 100) notify(app, "Overheating!", severity = "warning")
  }
)

# Multiple widgets from one key
reactive(
  count = list("display", ~ update(.app, "label", content = paste("N:", .x)))
)
} # }