exprToFunction: Convert an expression to a function

Description Usage Arguments Details Examples

View source: R/utils.R

Description

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

Usage

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

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?

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

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# 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")

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

## End(Not run)

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

isolate(tripleA())
# "text, text, text"

shiny documentation built on Aug. 24, 2017, 1:04 a.m.