Valentin Shergin dea8773c19 Fabric: ValueFactory and EventEmitter::dispatchEvent based on that
Summary:
Now the event delive pipeline supports `JSI::Value`-based payload. Instead of passing `folly::dynamic`, now we are passing `std::function<jsi::Value(jsi::Runtime &runtime)>` as factory that can build a `JSI::Value` with given `jsi::Runtime` and any captured data.
The old (now legacy) way of calling `EventEmitter::dispatchEvent(..., const folly::dynamic &payload, ...)` is also supported.

Reviewed By: sahrens

Differential Revision: D13123043

fbshipit-source-id: d65348bb215013042abb2fcfe5083a8c697333d0
2018-11-27 21:00:55 -08:00

101 lines
3.0 KiB
C++

/**
* Copyright (c) Facebook, Inc. and its affiliates.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*/
#pragma once
#include <memory>
#include <mutex>
#include <folly/dynamic.h>
#include <react/events/EventDispatcher.h>
#include <react/events/primitives.h>
namespace facebook {
namespace react {
class EventEmitter;
using SharedEventEmitter = std::shared_ptr<const EventEmitter>;
/*
* Base class for all particular typed event handlers.
* Stores a pointer to `EventTarget` identifying a particular component and
* a weak pointer to `EventDispatcher` which is responsible for delivering the
* event.
*
* Note: Retaining an `EventTarget` does *not* guarantee that actual event
* target exists and/or valid in JavaScript realm. The `EventTarget` retains an
* `EventTargetWrapper` which wraps JavaScript object in `unsafe-unretained`
* manner. Retaining the `EventTarget` *does* indicate that we can use that to
* get an actual JavaScript object from that in the future *ensuring safety
* beforehand somehow*; JSI maintains `WeakObject` object as long as we retain
* the `EventTarget`. All `EventTarget` instances must be deallocated before
* stopping JavaScript machine.
*/
class EventEmitter {
/*
* We have to repeat `Tag` type definition here because `events` module does
* not depend on `core` module (and should not).
*/
using Tag = int32_t;
public:
static std::recursive_mutex &DispatchMutex();
static ValueFactory defaultPayloadFactory();
EventEmitter(
SharedEventTarget eventTarget,
Tag tag,
WeakEventDispatcher eventDispatcher);
virtual ~EventEmitter() = default;
/*
* `DispatchMutex` must be acquired before calling.
* Enables/disables event emitter.
* Enabled event emitter retains a pointer to `eventTarget` strongly (as
* `std::shared_ptr`) whereas disabled one weakly (as `std::weak_ptr`).
* The enable state is additive; a number of `enable` calls should be equal to
* a number of `disable` calls to release the event target.
*/
void enable() const;
void disable() const;
protected:
#ifdef ANDROID
// We need this temporarily due to lack of Java-counterparts for particular
// subclasses.
public:
#endif
/*
* Initates an event delivery process.
* Is used by particular subclasses only.
*/
void dispatchEvent(
const std::string &type,
const ValueFactory &payloadFactory =
EventEmitter::defaultPayloadFactory(),
const EventPriority &priority = EventPriority::AsynchronousBatched) const;
void dispatchEvent(
const std::string &type,
const folly::dynamic &payload,
const EventPriority &priority = EventPriority::AsynchronousBatched) const;
private:
void toggleEventTargetOwnership_() const;
mutable SharedEventTarget eventTarget_;
mutable WeakEventTarget weakEventTarget_;
WeakEventDispatcher eventDispatcher_;
mutable int enableCounter_{0};
};
} // namespace react
} // namespace facebook