renderPrint.Rd

% Generated by roxygen2 (4.1.0): do not edit by hand
% Please edit documentation in R/shinywrappers.R
\name{renderPrint}
\alias{renderPrint}
\title{Printable Output}
\usage{
renderPrint(expr, env = parent.frame(), quoted = FALSE, func = NULL,
  width = getOption("width"))
}
\arguments{
\item{expr}{An expression that may print output and/or return a printable R
object.}

\item{env}{The environment in which to evaluate \code{expr}.}

\item{quoted}{Is \code{expr} a quoted expression (with \code{quote()})? This}

\item{func}{A function that may print output and/or return a printable R
object (deprecated; use \code{expr} instead).}

\item{width}{The value for \code{\link{options}('width')}.}
}
\description{
Makes a reactive version of the given function that captures any printed
output, and also captures its printable result (unless
\code{\link{invisible}}), into a string. The resulting function is suitable
for assigning to an  \code{output} slot.
}
\details{
The corresponding HTML output tag can be anything (though \code{pre} is
recommended if you need a monospace font and whitespace preserved) and should
have the CSS class name \code{shiny-text-output}.

The result of executing \code{func} will be printed inside a
\code{\link[utils]{capture.output}} call.

Note that unlike most other Shiny output functions, if the given function
returns \code{NULL} then \code{NULL} will actually be visible in the output.
To display nothing, make your function return \code{\link{invisible}()}.
}
\examples{
isolate({

# renderPrint captures any print output, converts it to a string, and
# returns it
visFun <- renderPrint({ "foo" })
visFun()
# '[1] "foo"'

invisFun <- renderPrint({ invisible("foo") })
invisFun()
# ''

multiprintFun <- renderPrint({
  print("foo");
  "bar"
})
multiprintFun()
# '[1] "foo"\\n[1] "bar"'

nullFun <- renderPrint({ NULL })
nullFun()
# 'NULL'

invisNullFun <- renderPrint({ invisible(NULL) })
invisNullFun()
# ''

vecFun <- renderPrint({ 1:5 })
vecFun()
# '[1] 1 2 3 4 5'


# Contrast with renderText, which takes the value returned from the function
# and uses cat() to convert it to a string
visFun <- renderText({ "foo" })
visFun()
# 'foo'

invisFun <- renderText({ invisible("foo") })
invisFun()
# 'foo'

multiprintFun <- renderText({
  print("foo");
  "bar"
})
multiprintFun()
# 'bar'

nullFun <- renderText({ NULL })
nullFun()
# ''

invisNullFun <- renderText({ invisible(NULL) })
invisNullFun()
# ''

vecFun <- renderText({ 1:5 })
vecFun()
# '1 2 3 4 5'

})
}
\seealso{
\code{\link{renderText}} for displaying the value returned from a
  function, instead of the printed output.
}