R/environment.R

In dturkenk/injectr: Dependency Injection for R

.injectr.container <- new.env(parent = emptyenv())

#' Register an object to inject
#'
#' @param object the object to inject
#' @param name the name to use for resolution. Defaults to the passed in object reference
#' @param generator whether the passed in object should be used as a generator function upon injection
#'
#' @export
register <- function(object, 
                    name = NULL,
                    generator = FALSE) {
    if (is.null(name)) {
        name <- as.character(substitute(object))
    }

    if(is.function(object) && startsWith(name, "function")) {
        stop("Anonymous functions cannot be registered")
    }

    wrapper <- .object_wrapper(object, "generator" = generator)

    assign(name, wrapper, envir = .injectr.container)
}

#' Inject an object from the container into a variable
#'
#' @param name the name of the object to inject
#'
#' @return the defined object or null
#'
#' @export
inject <- function(name, target = NULL) {

    wrapper <- get0(name, envir = .injectr.container)

    if (is.null(wrapper)) {

        error_on_no_match <- getOption("injectr.error_on_no_match")

        if (is.null(error_on_no_match)) {
            error_on_no_match <- FALSE
        }

        if (error_on_no_match) {
            stop(paste0("No object matching ", name, " found."))
        }

        return(invisible())
    }

    if (hasArg(target)) {
        name <- as.character(substitute(target))
    }

    if (!is.null(wrapper$generator) && wrapper$generator) {
        object <- wrapper$object()
    } else {
        object <- wrapper$object
    }

    assign(name, object, envir = parent.frame())
}

#' Clear the entire container
#'
#' @export
clear <- function() {
    rm(list = ls(envir = .injectr.container), envir = .injectr.container)
}

#' Wrapper for object to allow storing of arbitrary configuration information
.object_wrapper <- function(object, ...) {
    if (is.null(object)) stop("object must be provided")
    structure(list("object" = object, ...), class = "object_wrapper")
}