Convert an expression to a function
This is to be called from another function, because it will attempt to get
an unquoted expression from two calls back. Note: as of Shiny 1.6.0, it is
recommended to use quoToFunction() instead.
exprToFunction(expr, env = parent.frame(), quoted = FALSE)
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? |
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.
# 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"Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.