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Added spin_node_until_future_complete #25

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Apr 28, 2015
Merged

Added spin_node_until_future_complete #25

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90ba163
Added spin_node_until_future_complete
Apr 28, 2015
6b6b94f
Added comment about not being able to call spin_node_until_future_com…
Apr 28, 2015
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19 changes: 19 additions & 0 deletions rclcpp/include/rclcpp/executors.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -15,8 +15,11 @@
#ifndef RCLCPP_RCLCPP_EXECUTORS_HPP_
#define RCLCPP_RCLCPP_EXECUTORS_HPP_

#include <future>
#include <rclcpp/executors/multi_threaded_executor.hpp>
#include <rclcpp/executors/single_threaded_executor.hpp>
#include <rclcpp/node.hpp>
#include <rclcpp/utilities.hpp>

namespace rclcpp
{
Expand All @@ -26,6 +29,22 @@ namespace executors
using rclcpp::executors::multi_threaded_executor::MultiThreadedExecutor;
using rclcpp::executors::single_threaded_executor::SingleThreadedExecutor;

template<typename FutureT>
std::shared_future<FutureT> &
spin_node_until_future_complete(
rclcpp::executor::Executor & executor, rclcpp::node::Node::SharedPtr & node_ptr,
std::shared_future<FutureT> & future)
{
std::future_status status;
// TODO: does not work recursively right, can't call spin_node_until_future_complete
// inside a callback executed by an executor.
do {
executor.spin_node_some(node_ptr);
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It may be worth putting a TODO here mentioning that this won't work recursively right now, i.e. you can't call spin_node_until_future_complete inside a callback executed by an executor.

status = future.wait_for(std::chrono::seconds(0));
} while (status != std::future_status::ready && rclcpp::utilities::ok());
return future;
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Does it need to return the passed in future? What would be a use case for that?

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Doesn't need to, but it's convenient because one can write code like this:

auto value = spin_node_until_future_complete<int64_t>(executor, node, future).get();

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For method chaining I find it pretty _un_intuitive that the function returns the future. Especially since it looks like that passing a temporary future does not work.

I don't know if others have an opinion on this. We could always defer this to an API review in the future.

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The function already returns the future, what changes do you suggest?

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Not returning anything.

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For method chaining I find it pretty intuitive that the function returns the future

You meant intuitive or counter intuitive?

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I think it is fine as is, the method chaining looks useful and I don't see that it needs to return anything else.

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Sorry, important spelling error: I meant unintuitive.

The calling code has the future and it looks arbitrary and _un_intuitive to me why the method would return that specific argument for chaining.

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Supporting chaining operators make usage much more compact. The other option I see is to have an additional or overridden get method which will do the background spinning. But I think this is cleaner and doesn't require modifying builtins.

}

} // namespace executors
} // namespace rclcpp

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11 changes: 11 additions & 0 deletions rclcpp/include/rclcpp/rclcpp.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -76,6 +76,17 @@ void spin(Node::SharedPtr & node_ptr)
executor.spin();
}

template<typename FutureT>
std::shared_future<FutureT> &
spin_until_future_complete(
Node::SharedPtr & node_ptr, std::shared_future<FutureT> & future)
{
rclcpp::executors::SingleThreadedExecutor executor;
rclcpp::executors::spin_node_until_future_complete<FutureT>(
executor, node_ptr, future);
return future;
}

} /* namespace rclcpp */

#endif /* RCLCPP_RCLCPP_RCLCPP_HPP_ */