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dde266768c
These functions were temporarily ripped out of Shiny and moved to the htmltools package. We've discovered that it's safe to keep including them in shiny; as long as the functions in shiny and the functions in htmltools are identical, the user won't receive a conflict warning.
67 lines
2.1 KiB
R
67 lines
2.1 KiB
R
% Generated by roxygen2 (4.0.1): do not edit by hand
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\name{reactive}
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\alias{is.reactive}
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\alias{reactive}
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\title{Create a reactive expression}
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\usage{
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reactive(x, env = parent.frame(), quoted = FALSE, label = NULL,
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domain = getDefaultReactiveDomain())
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is.reactive(x)
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}
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\arguments{
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\item{x}{For \code{reactive}, an expression (quoted or unquoted). For
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\code{is.reactive}, an object to test.}
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\item{env}{The parent environment for the reactive expression. By default, this
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is the calling environment, the same as when defining an ordinary
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non-reactive expression.}
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\item{quoted}{Is the expression quoted? By default, this is \code{FALSE}.
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This is useful when you want to use an expression that is stored in a
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variable; to do so, it must be quoted with `quote()`.}
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\item{label}{A label for the reactive expression, useful for debugging.}
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\item{domain}{See \link{domains}.}
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}
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\value{
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a function, wrapped in a S3 class "reactive"
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}
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\description{
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Wraps a normal expression to create a reactive expression. Conceptually, a
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reactive expression is a expression whose result will change over time.
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}
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\details{
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Reactive expressions are expressions that can read reactive values and call other
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reactive expressions. Whenever a reactive value changes, any reactive expressions
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that depended on it are marked as "invalidated" and will automatically
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re-execute if necessary. If a reactive expression is marked as invalidated, any
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other reactive expressions that recently called it are also marked as
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invalidated. In this way, invalidations ripple through the expressions that
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depend on each other.
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See the \href{http://rstudio.github.com/shiny/tutorial/}{Shiny tutorial} for
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more information about reactive expressions.
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}
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\examples{
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values <- reactiveValues(A=1)
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reactiveB <- reactive({
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values$A + 1
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})
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# Can use quoted expressions
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reactiveC <- reactive(quote({ values$A + 2 }), quoted = TRUE)
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# To store expressions for later conversion to reactive, use quote()
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expr_q <- quote({ values$A + 3 })
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reactiveD <- reactive(expr_q, quoted = TRUE)
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# View the values from the R console with isolate()
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isolate(reactiveB())
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isolate(reactiveC())
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isolate(reactiveD())
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}
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