reactive: Reactive state fields

In termr: Modern Reactive Terminal Applications with Data Workflows

Reactive state fields

Description

reactive() declares a state field of a custom widget (see widget()). Reading the field returns its value; assigning a different value (self$count <- self$count + 1L) invalidates the widget and schedules a repaint. Repaints are batched: any number of assignments in one event-loop tick produce a single render and a single screen diff.

Usage

reactive(value = NULL, watch = NULL)

Arguments

value	Initial value.
watch	Optional ⁠function(self, value, old)⁠ called after the value changed, e.g. to post a message or update other widgets.

Value

An object of class termr_reactive.

Examples

reactive(0L)
reactive("", watch = function(self, value, old) message("now ", value))

termr documentation built on Oct. 21, 2026, 5:13 p.m.