138 lines
3.8 KiB
C++
138 lines
3.8 KiB
C++
// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
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#pragma once
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/*! \file rx-element_at.hpp
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\brief Pulls an item located at a specified index location in the sequence of items and emits that item as its own sole emission.
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\param index the index of the element to return.
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\return An observable that emit an item located at a specified index location.
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\sample
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\snippet element_at.cpp element_at sample
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\snippet output.txt element_at sample
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*/
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#if !defined(RXCPP_OPERATORS_RX_ELEMENT_AT_HPP)
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#define RXCPP_OPERATORS_RX_ELEMENT_AT_HPP
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#include "../rx-includes.hpp"
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namespace rxcpp {
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namespace operators {
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namespace detail {
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template<class... AN>
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struct element_at_invalid_arguments {};
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template<class... AN>
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struct element_at_invalid : public rxo::operator_base<element_at_invalid_arguments<AN...>> {
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using type = observable<element_at_invalid_arguments<AN...>, element_at_invalid<AN...>>;
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};
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template<class... AN>
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using element_at_invalid_t = typename element_at_invalid<AN...>::type;
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template<class T>
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struct element_at {
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typedef rxu::decay_t<T> source_value_type;
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struct element_at_values {
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element_at_values(int i)
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: index(i)
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{
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}
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int index;
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};
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element_at_values initial;
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element_at(int i)
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: initial(i)
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{
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}
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template<class Subscriber>
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struct element_at_observer : public element_at_values
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{
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typedef element_at_observer<Subscriber> this_type;
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typedef source_value_type value_type;
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typedef rxu::decay_t<Subscriber> dest_type;
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typedef observer<value_type, this_type> observer_type;
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dest_type dest;
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mutable int current;
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element_at_observer(dest_type d, element_at_values v)
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: element_at_values(v),
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dest(d),
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current(0)
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{
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}
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void on_next(source_value_type v) const {
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if (current++ == this->index) {
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dest.on_next(v);
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dest.on_completed();
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}
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}
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void on_error(rxu::error_ptr e) const {
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dest.on_error(e);
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}
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void on_completed() const {
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if(current <= this->index) {
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dest.on_error(rxu::make_error_ptr(std::range_error("index is out of bounds")));
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}
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}
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static subscriber<value_type, observer_type> make(dest_type d, element_at_values v) {
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return make_subscriber<value_type>(d, this_type(d, v));
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}
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};
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template<class Subscriber>
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auto operator()(Subscriber dest) const
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-> decltype(element_at_observer<Subscriber>::make(std::move(dest), initial)) {
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return element_at_observer<Subscriber>::make(std::move(dest), initial);
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}
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};
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}
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/*! @copydoc rx-element_at.hpp
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*/
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template<class... AN>
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auto element_at(AN&&... an)
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-> operator_factory<element_at_tag, AN...> {
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return operator_factory<element_at_tag, AN...>(std::make_tuple(std::forward<AN>(an)...));
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}
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}
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template<>
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struct member_overload<element_at_tag>
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{
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template<class Observable,
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class Enabled = rxu::enable_if_all_true_type_t<
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is_observable<Observable>
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>,
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class SourceValue = rxu::value_type_t<Observable>,
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class element_at = rxo::detail::element_at<SourceValue>>
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static auto member(Observable&& o, int index)
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-> decltype(o.template lift<SourceValue>(element_at(index))) {
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return o.template lift<SourceValue>(element_at(index));
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}
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template<class... AN>
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static operators::detail::element_at_invalid_t<AN...> member(const AN...) {
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std::terminate();
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return {};
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static_assert(sizeof...(AN) == 10000, "element_at takes (required int)");
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}
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};
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}
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#endif
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