For reactive, an expression (quoted or unquoted). For
is.reactive, an object to test.
env
The parent environment for the reactive expression. By default,
this is the calling environment, the same as when defining an ordinary
non-reactive expression.
quoted
Is the expression quoted? By default, this is FALSE.
This is useful when you want to use an expression that is stored in a
variable; to do so, it must be quoted with quote().
label
A label for the reactive expression, useful for debugging.
domain
See domains.
..stacktraceon
Advanced use only. For stack manipulation purposes; see
stacktrace.
Details
Reactive expressions are expressions that can read reactive values and call
other reactive expressions. Whenever a reactive value changes, any reactive
expressions that depended on it are marked as "invalidated" and will
automatically re-execute if necessary. If a reactive expression is marked as
invalidated, any other reactive expressions that recently called it are also
marked as invalidated. In this way, invalidations ripple through the
expressions that depend on each other.
See the Shiny tutorial for
more information about reactive expressions.
Value
a function, wrapped in a S3 class "reactive"
Examples
values <- reactiveValues(A=1)
reactiveB <- reactive({
values$A + 1
})
# Can use quoted expressions
reactiveC <- reactive(quote({ values$A + 2 }), quoted = TRUE)
# To store expressions for later conversion to reactive, use quote()
expr_q <- quote({ values$A + 3 })
reactiveD <- reactive(expr_q, quoted = TRUE)
# View the values from the R console with isolate()
isolate(reactiveB())
isolate(reactiveC())
isolate(reactiveD())