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Convert an expression to a function

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?


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


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 # }) ## --------------------------------------------- # 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"