R/build_query_string.R

In AdamCottrill/GLFishStockR: Fetch Data From The Great Lakes Fish Stocking API

##' Given a list of filters return a url query string
##'
##' Given a list of filters (key-value pairs), this functions returns
##' a url query string that can be applied to an api
##' endpoint. Multiple list elements are separated by a '&' and list
##' elements with multiple values are returned as comma separated
##' values.
##'
##' @param filters list
##' @author Adam Cottrill \email{adam.cottrill@@ontario.ca}
##' @export
##' @return
##' A formatted string that matches the url search parameters
##' @examples
##' # return "?size=sm"
##' build_query_string(list(size="sm"))
##' # return "?colour=red,blue"
##' build_query_string(list(colours=c("red","blue")))
##' # return "?size=sm&colour=red,blue"
##' build_query_string(list(size='sm', colours=c("red","blue")))
##'
##'
build_query_string <- function(filters) {
  if (length(filters) == 0) {
    return("")
  } else {
    qs <- paste(names(filters), sapply(filters, paste, collapse = ","),
      sep = "=", collapse = "&"
    )
  }
  return(sprintf("?%s", qs))
}