paleolimbot commented on code in PR #12817:
URL: https://github.com/apache/arrow/pull/12817#discussion_r854344830
##########
r/R/array.R:
##########
@@ -217,6 +217,125 @@ Array$create <- function(x, type = NULL) {
Array$import_from_c <- ImportArray
+#' Convert an object to an Arrow Array
+#'
+#' Whereas `Array$create()` constructs an [Array] from the built-in data types
+#' for which the Arrow package implements fast converters, `as_arrow_array()`
+#' provides a means by which other packages can define conversions to Arrow
+#' objects.
+#'
+#' @param x An object to convert to an Arrow Array
+#' @param ... Passed to S3 methods
+#' @param type A [type][data-type] for the final Array. A value of `NULL`
+#' will default to the type guessed by [type()].
+#'
+#' @return An [Array].
+#' @export
+#'
+#' @examplesIf arrow_available()
+#' as_arrow_array(1:5)
+#'
+as_arrow_array <- function(x, ..., type = NULL) {
+ UseMethod("as_arrow_array")
+}
+
+#' @rdname as_arrow_array
+#' @export
+as_arrow_array.Array <- function(x, ..., type = NULL) {
+ if (is.null(type)) {
+ x
+ } else {
+ x$cast(type)
+ }
+}
+
+#' @rdname as_arrow_array
+#' @export
+as_arrow_array.ChunkedArray <- function(x, ..., type = NULL) {
+ concat_arrays(!!! x$chunks, type = type)
+}
+
+#' @rdname as_arrow_array
+#' @export
+as_arrow_array.vctrs_vctr <- function(x, ..., type = NULL) {
+ if (is.null(type)) {
+ vctrs_extension_array(x)
+ } else if (inherits(type, "VctrsExtensionType")) {
+ vctrs_extension_array(
+ x,
+ ptype = type$ptype(),
+ storage_type = type$storage_type()
+ )
+ } else {
+ stop_cant_convert_array(x, type)
+ }
+}
+
+#' @export
+as_arrow_array.POSIXlt <- function(x, ..., type = NULL) {
+ as_arrow_array.vctrs_vctr(x, ..., type = type)
+}
+
+#' @export
+as_arrow_array.data.frame <- function(x, ..., type = NULL) {
+ type <- type %||% infer_type(x)
+
+ if (inherits(type, "VctrsExtensionType")) {
+ storage <- as_arrow_array(x, type = type$storage_type())
+ new_extension_array(storage, type)
+ } else if (inherits(type, "StructType")) {
+ fields <- type$fields()
+ names <- map_chr(fields, "name")
+ types <- map(fields, "type")
+ arrays <- Map(as_arrow_array, x, types)
+ names(arrays) <- names
+
+ # ...because there isn't a StructArray$create() yet
+ batch <- record_batch(!!! arrays)
+ array_ptr <- allocate_arrow_array()
+ schema_ptr <- allocate_arrow_schema()
+ batch$export_to_c(array_ptr, schema_ptr)
+ Array$import_from_c(array_ptr, schema_ptr)
+ } else {
+ stop_cant_convert_array(x, type)
+ }
+}
+
+#' @export
+as_arrow_array.default <- function(x, ..., type = NULL, from_constructor =
FALSE) {
+ # If from_constructor is TRUE, this is a call from C++ for which S3 dispatch
+ # failed to find a method for the object. If this is the case, we error.
Review Comment:
Yes! I added that to the comment (and to the one in type.R).
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
