Class output of reactive.

Also add print method and test

NAMESPACE

@@ -17,6 +17,7 @@ S3method(as.list,reactivevalues)
 S3method(format,shiny.tag)
 S3method(format,shiny.tag.list)
 S3method(names,reactivevalues)
+S3method(print,reactive)
 S3method(print,shiny.tag)
 S3method(print,shiny.tag.list)
 export(HTML)
@@ -57,6 +58,7 @@ export(includeMarkdown)
 export(includeScript)
 export(includeText)
 export(invalidateLater)
+export(is.reactive)
 export(isolate)
 export(mainPanel)
 export(numericInput)

R/reactives.R

@@ -369,14 +369,16 @@ Observable <- setRefClass(
 #' See the \href{http://rstudio.github.com/shiny/tutorial/}{Shiny tutorial} for
 #' more information about reactive expressions.
 #'
-#' @param x An expression (quoted or unquoted).
+#' @param x For \code{reactive}, an expression (quoted or unquoted). For 
+#'   \code{is.reactive}, an object to test.
 #' @param 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.
 #' @param quoted Is the expression quoted? By default, this is \code{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()`.
 #' @param label A label for the reactive expression, useful for debugging.
+#' @return a function, wrapped in a S3 class "reactive"
 #'
 #' @examples
 #' values <- reactiveValues(A=1)
@@ -403,9 +405,20 @@ reactive <- function(x, env = parent.frame(), quoted = FALSE, label = NULL) {
   if (is.null(label))
     label <- sprintf('reactive(%s)', paste(deparse(body(fun)), collapse='\n'))
 
-  Observable$new(fun, label)$getValue
+  o <- Observable$new(fun, label)
+  structure(o$getValue@.Data, observable = o, class = "reactive")
 }
 
+#' @S3method print reactive
+print.reactive <- function(x, ...) {
+  label <- attr(x, "observable")$.label
+  cat(label, "\n")
+}
+
+#' @export
+#' @rdname reactive
+is.reactive <- function(x) inherits(x, "reactive")
+
 # Return the number of times that a reactive expression or observer has been run
 execCount <- function(x) {
   if (is.function(x))

man/reactive.Rd

@@ -1,12 +1,16 @@
 \name{reactive}
+\alias{is.reactive}
 \alias{reactive}
 \title{Create a reactive expression}
 \usage{
   reactive(x, env = parent.frame(), quoted = FALSE,
     label = NULL)
+
+  is.reactive(x)
 }
 \arguments{
-  \item{x}{An expression (quoted or unquoted).}
+  \item{x}{For \code{reactive}, an expression (quoted or
+  unquoted). For \code{is.reactive}, an object to test.}
 
   \item{env}{The parent environment for the reactive
   expression. By default, this is the calling environment,
@@ -21,6 +25,9 @@
   \item{label}{A label for the reactive expression, useful
   for debugging.}
 }
+\value{
+  a function, wrapped in a S3 class "reactive"
+}
 \description{
   Wraps a normal expression to create a reactive
   expression. Conceptually, a reactive expression is a