actor_ref.hpp

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#pragma once
 
#include <mbgl/actor/mailbox.hpp>
#include <mbgl/actor/message.hpp>
 
#include <memory>
 
namespace mbgl {
 
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