Convert an expression to a function

exprToFunction(expr, env = parent.frame(2), quoted = FALSE, caller_offset = 1)

Arguments

expr A quoted or unquoted expression, or a function.
env The desired environment for the function. Defaults to the calling environment two steps back.
quoted Is the expression quoted?
caller_offset If specified, the offset in the callstack of the functiont to be treated as the caller.

Convert an expression to a function

Description

This is to be called from another function, because it will attempt to get an unquoted expression from two calls back.

Details

If expr is a quoted expression, then this just converts it to a function. If expr is a function, then this simply returns expr (and prints a deprecation message). If expr was a non-quoted expression from two calls back, then this will quote the original expression and convert it to a function.

Examples

# Example of a new renderer, similar to renderText
# This is something that toolkit authors will do
renderTriple <- function(expr, env=parent.frame(), quoted=FALSE) {
  # Convert expr to a function
  func <- shiny::exprToFunction(expr, env, quoted)

  function() {
    value <- func()
    paste(rep(value, 3), collapse=", ")
  }
}


# Example of using the renderer.
# This is something that app authors will do.
values <- reactiveValues(A="text")

## <strong>Not run</strong>: 
# # Create an output object
# output$tripleA <- renderTriple({
#   values$A
# })
# ## <strong>End(Not run)</strong>

# At the R console, you can experiment with the renderer using isolate()
tripleA <- renderTriple({
  values$A
})

isolate(tripleA())



[1] "text, text, text"



# "text, text, text"