61 lines
1.9 KiB
C++
61 lines
1.9 KiB
C++
#pragma once
|
|
|
|
#include <mbgl/actor/mailbox.hpp>
|
|
#include <mbgl/actor/message.hpp>
|
|
|
|
#include <memory>
|
|
|
|
namespace mbgl {
|
|
|
|
/**
|
|
An `ActorRef<O>` is a *non*-owning, weak reference to an actor of type `O`.
|
|
You can send it messages just like an `Actor<O>`. It's a value object: safe
|
|
to copy and pass between actors via messages.
|
|
|
|
An `ActorRef<O>` does not extend the lifetime of the corresponding
|
|
`Actor<O>`. That's determined entirely by whichever object owns the
|
|
`Actor<O>` -- the actor's "supervisor".
|
|
|
|
It's safe for a `Ref` to outlive its `Actor` -- the reference is "weak", and
|
|
does not extend the lifetime of the owning Actor, and sending a message to a
|
|
`Ref` whose `Actor` has died is a no-op. (In the future, a dead-letters queue
|
|
or log may be implemented.)
|
|
*/
|
|
template <class Object>
|
|
class ActorRef {
|
|
public:
|
|
ActorRef(Object& object_, std::weak_ptr<Mailbox> weakMailbox_)
|
|
: object(&object_),
|
|
weakMailbox(std::move(weakMailbox_)) {}
|
|
|
|
template <typename Fn, class... Args>
|
|
void invoke(Fn fn, Args&&... args) const {
|
|
if (auto mailbox = weakMailbox.lock()) {
|
|
mailbox->push(actor::makeMessage(*object, fn, std::forward<Args>(args)...));
|
|
}
|
|
}
|
|
|
|
template <typename Fn, class... Args>
|
|
auto ask(Fn fn, Args&&... args) const {
|
|
// Result type is deduced from the function's return type
|
|
using ResultType = std::invoke_result_t<decltype(fn), Object, Args...>;
|
|
|
|
std::promise<ResultType> promise;
|
|
auto future = promise.get_future();
|
|
|
|
if (auto mailbox = weakMailbox.lock()) {
|
|
mailbox->push(actor::makeMessage(std::move(promise), *object, fn, std::forward<Args>(args)...));
|
|
} else {
|
|
promise.set_exception(std::make_exception_ptr(std::runtime_error("Actor has gone away")));
|
|
}
|
|
|
|
return future;
|
|
}
|
|
|
|
private:
|
|
Object* object;
|
|
std::weak_ptr<Mailbox> weakMailbox;
|
|
};
|
|
|
|
} // namespace mbgl
|