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#' Retrieve an attribute.
#'
#' `xml_attrs()` retrieves all attributes values as a named character
#' vector, `xml_attrs() <-` or `xml_set_attrs()` sets all attribute
#' values. `xml_attr()` retrieves the value of single attribute and
#' `xml_attr() <-` or `xml_set_attr()` modifies its value. If the
#' attribute doesn't exist, it will return `default`, which defaults to
#' `NA`. `xml_has_attr()` tests if an attribute is present.
#'
#' @inheritParams xml_name
#' @param attr Name of attribute to extract.
#' @param default Default value to use when attribute is not present.
#' @return `xml_attr()` returns a character vector. `NA` is used
#' to represent of attributes that aren't defined.
#'
#' `xml_has_attr()` returns a logical vector.
#'
#' `xml_attrs()` returns a named character vector if `x` x is single
#' node, or a list of character vectors if given a nodeset
#' @export
#' @examples
#' x <- read_xml("<root id='1'><child id ='a' /><child id='b' d='b'/></root>")
#' xml_attr(x, "id")
#' xml_attr(x, "apple")
#' xml_attrs(x)
#'
#' kids <- xml_children(x)
#' kids
#' xml_attr(kids, "id")
#' xml_has_attr(kids, "id")
#' xml_attrs(kids)
#'
#' # Missing attributes give missing values
#' xml_attr(xml_children(x), "d")
#' xml_has_attr(xml_children(x), "d")
#'
#' # If the document has a namespace, use the ns argument and
#' # qualified attribute names
#' x <- read_xml('
#' <root xmlns:b="http://bar.com" xmlns:f="http://foo.com">
#' <doc b:id="b" f:id="f" id="" />
#' </root>
#' ')
#' doc <- xml_children(x)[[1]]
#' ns <- xml_ns(x)
#'
#' xml_attrs(doc)
#' xml_attrs(doc, ns)
#'
#' # If you don't supply a ns spec, you get the first matching attribute
#' xml_attr(doc, "id")
#' xml_attr(doc, "b:id", ns)
#' xml_attr(doc, "id", ns)
#'
#' # Can set a single attribute with `xml_attr() <-` or `xml_set_attr()`
#' xml_attr(doc, "id") <- "one"
#' xml_set_attr(doc, "id", "two")
#'
#' # Or set multiple attributes with `xml_attrs()` or `xml_set_attrs()`
#' xml_attrs(doc) <- c("b:id" = "one", "f:id" = "two", "id" = "three")
#' xml_set_attrs(doc, c("b:id" = "one", "f:id" = "two", "id" = "three"))
xml_attr <- function(x, attr, ns = character(), default = NA_character_) {
UseMethod("xml_attr")
}
#' @export
xml_attr.xml_missing <- function(x, attr, ns = character(), default = NA_character_) {
default
}
#' @export
xml_attr.xml_node <- function(x, attr, ns = character(),
default = NA_character_) {
.Call(node_attr, x$node, attr, as.character(default), ns)
}
#' @export
xml_attr.xml_nodeset <- function(x, attr, ns = character(),
default = NA_character_) {
vapply(x, xml_attr, attr = attr, default = default, ns = ns,
FUN.VALUE = character(1))
}
#' @export
#' @rdname xml_attr
xml_has_attr <- function(x, attr, ns = character()) {
!is.na(xml_attr(x, attr, ns = ns))
}
#' @export
#' @rdname xml_attr
xml_attrs <- function(x, ns = character()) {
UseMethod("xml_attrs")
}
#' @export
xml_attrs.xml_missing <- function(x, ns = character()) {
NA_character_
}
#' @export
xml_attrs.xml_node <- function(x, ns = character()) {
.Call(node_attrs, x$node, nsMap = ns)
}
#' @export
xml_attrs.xml_nodeset <- function(x, ns = character()) {
lapply(x, xml_attrs, ns = ns)
}
#' @param value character vector of new value.
#' @rdname xml_attr
#' @export
`xml_attr<-` <- function(x, attr, ns = character(), value) {
UseMethod("xml_attr<-")
}
#' @export
`xml_attr<-.xml_node` <- function(x, attr, ns = character(), value) {
if (is.null(value)) {
.Call(node_remove_attr, x$node, attr, ns)
} else {
value <- as.character(value)
.Call(node_set_attr, x$node, attr, value, ns)
}
x
}
#' @export
`xml_attr<-.xml_nodeset` <- function(x, attr, ns = character(), value) {
if (length(x) == 0) {
return(x)
}
if (length(value) == 0) {
value <- list(value)
}
mapply(`xml_attr<-`, x, attr = attr, value = value, SIMPLIFY = FALSE, MoreArgs = list(ns = ns))
x
}
#' @export
`xml_attr<-.xml_missing` <- function(x, attr, ns = character(), value) {
x
}
#' @rdname xml_attr
#' @export
xml_set_attr <- function(x, attr, value, ns = character()) {
UseMethod("xml_set_attr")
}
# This function definition is used for all methods, we need to rearrange the `ns`
# argument to be at the end of the set function
set_attr_fun <- function(x, attr, value, ns = character()) {
xml_attr(x = x, attr = attr, ns = ns) <- value
}
#' @export
xml_set_attr.xml_node <- set_attr_fun
#' @export
xml_set_attr.xml_nodeset <- set_attr_fun
#' @export
xml_set_attr.xml_missing <- set_attr_fun
#' @rdname xml_attr
#' @export
`xml_attrs<-` <- function(x, ns = character(), value) {
UseMethod("xml_attrs<-")
}
#' @export
`xml_attrs<-.xml_node` <- function(x, ns = character(), value) {
if (!is_named(value)) {
stop("`value` must be a named character vector or `NULL`", call. = FALSE)
}
attrs <- names(value)
# as.character removes all attributes (including names)
value <- stats::setNames(as.character(value), attrs)
current_attrs <- names(xml_attrs(x, ns = ns))
existing <- intersect(current_attrs, attrs)
new <- setdiff(attrs, current_attrs)
removed <- setdiff(current_attrs, attrs)
# replace existing attributes and add new ones
Map(function(attr, val) {
xml_attr(x, attr, ns) <- val
}, attr = c(existing, new), value[c(existing, new)])
# Remove attributes which no longer exist
Map(function(attr) {
xml_attr(x, attr, ns) <- NULL
}, attr = removed)
x
}
#' @export
`xml_attrs<-.xml_nodeset` <- function(x, ns = character(), value) {
if (length(x) == 0) {
return(x)
}
if (!is.list(ns)) {
ns <- list(ns)
}
if (!is.list(value)) {
value <- list(value)
}
if (!all(vapply(value, is_named, logical(1)))) {
stop("`value` must be a list of named character vectors")
}
Map(`xml_attrs<-`, x, ns, value)
x
}
#' @export
`xml_attrs<-.xml_missing` <- function(x, ns = character(), value) {
x
}
#' @rdname xml_attr
#' @export
xml_set_attrs <- function(x, value, ns = character()) {
UseMethod("xml_set_attrs")
}
# This function definition is used for all methods, we need to rearrange the `ns`
# argument to be at the end of the set function
set_attrs_fun <- function(x, value, ns = character()) {
xml_attrs(x = x, ns = ns) <- value
}
#' @export
xml_set_attrs.xml_node <- set_attrs_fun
#' @export
xml_set_attrs.xml_nodeset <- set_attrs_fun
#' @export
xml_set_attrs.xml_missing <- set_attrs_fun
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