Source Specific Objects from Script

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.

Note that the source_selection() function does not suppress output (i.e. plots, prints, messages) from the sourced script file.

Usage

source_selection(lst, select = NULL, regex = NULL, fixed = NULL)

Arguments

lst

a named list, giving the arguments to be passed to the source function.
The local argument should not be included in the list.

select

a character vector, giving the exact names of the functions or objects appearing in the script, to expose to the current environment.

regex

a character vector of regex patterns (see about_search_regex).
These should give regular expressions that match to the names of the functions or objects appearing in the script, to expose to the current environment.
For example, to expose the following methods to the current environment,
mymethod.numeric() and mymethod.character() from generic mymethod(),
one could specify regex = "^mymethod".

fixed

a character vector of fixed patterns (see about_search_fixed).
These should give fixed expressions that match to the names of the functions or objects appearing in the script, to expose to the current environment.
For example, to expose the following methods to the current environment,
mymethod.numeric() and mymethod.character() from generic mymethod(),
one could specify fixed = "mymethod".

Value

Any specified objects will be placed in the current environment.

Details

One can specify which objects to expose using arguments select, regex, or fixed.
The user can specify all 3 of them, but at least one of the 3 must be specified.
It is not a problem if the specifications overlap.

See also

tinycodet_misc, base::source()

Examples

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")
})

source_selection(list(exprs=exprs), regex = "^mymethod")
#> Sourcing script ... 
#> Done
mymethod(1)
#> [1] 2
mymethod("a")
#> [1] "A"


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"