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We don't think anyone is using the freeze functions in the ways that we are deprecating, if so they should contact us via the link provided. If it turns out nobody complains, we can remove the problematic functions. If people complain, then we'll find out what they're using them for and we can fix them properly.
70 lines
2.4 KiB
R
70 lines
2.4 KiB
R
% Generated by roxygen2: do not edit by hand
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% Please edit documentation in R/reactives.R
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\name{freezeReactiveVal}
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\alias{freezeReactiveVal}
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\alias{freezeReactiveValue}
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\title{Freeze a reactive value}
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\usage{
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freezeReactiveVal(x)
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freezeReactiveValue(x, name)
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}
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\arguments{
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\item{x}{For \code{freezeReactiveValue}, a \code{\link[=reactiveValues]{reactiveValues()}}
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object (like \code{input}); for \code{freezeReactiveVal}, a
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\code{\link[=reactiveVal]{reactiveVal()}} object.}
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\item{name}{The name of a value in the \code{\link[=reactiveValues]{reactiveValues()}} object.}
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}
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\description{
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These functions freeze a \code{\link[=reactiveVal]{reactiveVal()}}, or an element of a
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\code{\link[=reactiveValues]{reactiveValues()}}. If the value is accessed while frozen, a
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"silent" exception is raised and the operation is stopped. This is the same
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thing that happens if \code{req(FALSE)} is called. The value is thawed
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(un-frozen; accessing it will no longer raise an exception) when the current
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reactive domain is flushed. In a Shiny application, this occurs after all of
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the observers are executed. \strong{NOTE:} We are considering deprecating
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\code{freezeReactiveVal}, and \code{freezeReactiveValue} except when \code{x} is \code{input}.
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If this affects your app, please let us know by leaving a comment on
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\href{https://github.com/rstudio/shiny/issues/3063}{this GitHub issue}.
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}
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\examples{
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## Only run this examples in interactive R sessions
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if (interactive()) {
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ui <- fluidPage(
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selectInput("data", "Data Set", c("mtcars", "pressure")),
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checkboxGroupInput("cols", "Columns (select 2)", character(0)),
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plotOutput("plot")
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)
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server <- function(input, output, session) {
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observe({
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data <- get(input$data)
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# Sets a flag on input$cols to essentially do req(FALSE) if input$cols
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# is accessed. Without this, an error will momentarily show whenever a
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# new data set is selected.
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freezeReactiveValue(input, "cols")
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updateCheckboxGroupInput(session, "cols", choices = names(data))
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})
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output$plot <- renderPlot({
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# When a new data set is selected, input$cols will have been invalidated
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# above, and this will essentially do the same as req(FALSE), causing
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# this observer to stop and raise a silent exception.
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cols <- input$cols
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data <- get(input$data)
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if (length(cols) == 2) {
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plot(data[[ cols[1] ]], data[[ cols[2] ]])
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}
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})
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}
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shinyApp(ui, server)
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}
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}
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\seealso{
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\code{\link[=req]{req()}}
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}
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