r/R/dictionary.R

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#' @include type.R

#' @title class DictionaryType
#'
#' @usage NULL
#' @format NULL
#' @docType class
#'
#' @section Methods:
#'
#' TODO
#'
#' @rdname DictionaryType
#' @name DictionaryType
DictionaryType <- R6Class("DictionaryType",
  inherit = FixedWidthType,
  public = list(
    ToString = function() {
      prettier_dictionary_type(DataType__ToString(self))
    }
  ),
  active = list(
    index_type = function() DataType$create(DictionaryType__index_type(self)),
    value_type = function() DataType$create(DictionaryType__value_type(self)),
    name = function() DictionaryType__name(self),
    ordered = function() DictionaryType__ordered(self)
  )
)
DictionaryType$create <- function(index_type = int32(),
                                  value_type = utf8(),
                                  ordered = FALSE) {
  assert_is(index_type, "DataType")
  assert_is(value_type, "DataType")
  shared_ptr(DictionaryType, DictionaryType__initialize(index_type, value_type, ordered))
}

#' Create a dictionary type
#'
#' @param index_type A DataType for the indices (default [int32()])
#' @param value_type A DataType for the values (default [utf8()])
#' @param ordered Is this an ordered dictionary (default `FALSE`)?
#'
#' @return A [DictionaryType]
#' @seealso [Other Arrow data types][data-type]
#' @export
dictionary <- DictionaryType$create

prettier_dictionary_type <- function(x) {
  # Prettier format the "ordered" attribute
  x <- sub(", ordered=0", "", x)
  sub("ordered=1", "ordered", x)
}