source_selection

The source_selection() function is the same as base R’s source() function, except that it allows only placing the selected objects and functions into the current environment, instead of all objects.

The objects to be selected can be specified using any combination of the following:

by supplying a character vector of exact object names to the select argument.
by supplying a character vector of regex patterns to the regex argument.
by supplying a character vector of fixed patterns to the fixed argument.

The regex and fixed arguments are especially handy when sourcing S3 methods. For example, to expose the following methods to the current environment, mymethod.numeric() and mymethod.character() from generic mymethod(), one could specify regex = "^mymethod".

Example:

exprs <- expression({
  helloworld = function()print("helloworld")
  goodbyeworld <- function() print("goodbye world")
  `%s+test%` <- function(x,y) stringi::`%s+%`(x,y)
  `%s*test%` <- function(x,y) stringi::`%s*%`(x,y)
  mymethod <- function(x) UseMethod("mymethod", x)
  mymethod.numeric <- function(x)x * 2
  mymethod.character <- function(x)chartr(x, old = "a-zA-Z", new = "A-Za-z")
})

temp.fun <- function(){
  source_selection(list(exprs=exprs), regex= "^mymethod", fixed = c("%", ":="))
  ls() # list all objects residing within the function definition
}
temp.fun()
#> Sourcing script ...
#> Done
#> [1] "%s*test%"           "%s+test%"           "mymethod"          
#> [4] "mymethod.character" "mymethod.numeric"

temp.fun <- function(){
  source_selection(list(exprs=exprs), select = c("helloworld", "goodbyeworld"))
  ls() # list all objects residing within the function definition
}
temp.fun()
#> Sourcing script ... 
#> 
#> Done
#> [1] "goodbyeworld" "helloworld"

Miscellaneous functionality

source_selection