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Documentation to come in a later PR Co-authored-by: Barret Schloerke <schloerke@gmail.com> Co-authored-by: Winston Chang <winston@stdout.org>
120 lines
4.3 KiB
R
120 lines
4.3 KiB
R
% Generated by roxygen2: do not edit by hand
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% Please edit documentation in R/utils-lang.R
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\name{quoToFunction}
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\alias{quoToFunction}
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\alias{sustainEnvAndQuoted}
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\title{Convert a quosure to a function for a Shiny render function}
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\usage{
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quoToFunction(q, label = sys.call(-1)[[1]], ..stacktraceon = FALSE)
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sustainEnvAndQuoted(q, x, env, quoted)
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}
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\arguments{
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\item{q}{A quosure.}
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\item{label}{A label for the object to be shown in the debugger. Defaults to
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the name of the calling function.}
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\item{..stacktraceon}{Advanced use only. For stack manipulation purposes; see
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\code{\link[=stacktrace]{stacktrace()}}.}
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\item{x}{An expression or quosure.}
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\item{env}{An environment. This is provided for backward compatibility.}
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\item{quoted}{A boolean indicating whether or not \code{env} is quoted. This is
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provided for backward compatibility.}
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}
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\description{
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This takes a quosure and label, and wraps them into a function that should be
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passed to \code{\link[=createRenderFunction]{createRenderFunction()}} or \code{\link[=markRenderFunction]{markRenderFunction()}}.
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\code{handleEnvAndQuoted()} and \code{quoToFunction()} are meant to be used together in a
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\code{render} function, to capture user expressions or quosures and convert them
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to functions. They are meant to replace the older functions
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\code{\link[=installExprFunction]{installExprFunction()}} and \code{\link[=exprToFunction]{exprToFunction()}} (although those will continue
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to work in the future). See the examples in \code{\link[=installExprFunction]{installExprFunction()}} for
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information on how to migrate to \code{getQuosure()} and \code{quoToFunction()}.
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}
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\details{
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This function was added in Shiny 1.6.0. Previously, it was recommended to use
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\code{\link[=installExprFunction]{installExprFunction()}} or \code{\link[=exprToFunction]{exprToFunction()}} in render functions, but now we
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recommend using \code{\link[=quoToFunction]{quoToFunction()}}, because it does not require \code{env} and
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\code{quoted} arguments -- that information is captured by quosures provided by
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\pkg{rlang}.
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Although \code{getQuosure()} can take \code{env} and \code{quoted} parameters, it is
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recommended that they not be used, except for backward compatibility.
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The recommended usage of \code{getQuosure()} and \code{quoToFunction()} does not
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include use of the \code{env} and \code{quoted} parameters. If it is necessary to
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use quoted expressions and/or custom environments for evaluating, it can be
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done with quosures and \code{\link[rlang:inject]{rlang::inject()}}. The examples below demonstrate how
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to do this.
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If you are updating from \code{\link[=installExprFunction]{installExprFunction()}} or \code{\link[=exprToFunction]{exprToFunction()}} to
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these functions, see the examples in the documentation for the old functions
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for how to migrate them.
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}
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\examples{
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# Example of a new renderer, similar to renderText.
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# This is something that toolkit authors will do.
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renderTriple <- function(expr) {
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# Convert expr to a quosure, and then to a function
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func <- quoToFunction(rlang::enquo0(expr))
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# Wrap up func, with another function which takes the value of func()
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# and modifies it.
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createRenderFunction(
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func,
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transform = function(value, session, name, ...) {
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paste(rep(value, 3), collapse=", ")
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},
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# The outputFunc can be used by rmarkdown shiny apps to automatically
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# generate outputs.
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outputFunc = textOutput
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)
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}
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# Example of using the renderer.
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# This is something that app authors will do.
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values <- reactiveValues(A="text")
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\dontrun{
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# Create an output object
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output$tripleA <- renderTriple({
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values$A
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})
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}
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# At the R console, you can experiment with the renderer using isolate()
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tripleA <- renderTriple({
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values$A
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})
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isolate(tripleA())
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# "text, text, text"
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# If you want to use a quoted expression, use rlang:inject().
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a <- 1
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expr <- quote({ values$A })
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tripleA <- rlang::inject(renderTriple(!!expr))
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isolate(tripleA())
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# "text, text, text"
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# Capturing an expression and an environment, using a quosure and rlang::inject():
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e <- new.env()
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e$vals <- reactiveValues(A="hello")
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# Create a quosure that captures both the expression and environment.
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myquo <- rlang::new_quosure(quote({ vals$A }), env = e)
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tripleA <- rlang::inject(renderTriple(!!myquo))
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isolate(tripleA())
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# "hello, hello, hello"
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}
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\seealso{
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\code{\link[=createRenderFunction]{createRenderFunction()}} for example usage.
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}
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