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8d83d5f8eb
Summary: I read my code and one thing stroke me: What if the same event emitter dispatches several events during the same event beat? In the previous implementation, only the first one will be delivered because the first `release` call consumes stored strong reference. So, I changed the API a bit to make this more explicit: we have `retain` & `release` methods and we have a getter that works (multiple times) only if the object was successfully retained. Reviewed By: sahrens Differential Revision: D13668147 fbshipit-source-id: c00af5f15bc7e30aa704d46bd23584b918b6f75a
78 lines
2.2 KiB
C++
78 lines
2.2 KiB
C++
/**
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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#pragma once
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#include <memory>
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#include <jsi/jsi.h>
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namespace facebook {
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namespace react {
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/*
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* `EventTarget` represents storage of a weak instance handle object with some
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* information about the possibility of retaining that strongly on demand.
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* Note: Retaining an `EventTarget` does *not* guarantee that actual event
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* target (a JavaScript object) is retaining and/or valid in JavaScript realm.
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* The `EventTarget` retains an `instanceHandle` value in `unsafe-unretained`
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* manner.
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* All `EventTarget` instances must be deallocated before
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* stopping JavaScript machine.
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*/
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class EventTarget {
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public:
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/*
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* We have to repeat `Tag` type definition here because `events` module does
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* not depend on `core` module (and should not).
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*/
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using Tag = int32_t;
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/*
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* Constructs an EventTarget from a weak instance handler and a tag.
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*/
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EventTarget(jsi::Runtime &runtime, const jsi::Value &instanceHandle, Tag tag);
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/*
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* Sets the `enabled` flag that allows creating a strong instance handle from
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* a weak one.
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*/
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void setEnabled(bool enabled) const;
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/*
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* Retains an instance handler by creating a strong reference to it.
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* If the EventTarget is disabled, does nothing.
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*/
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void retain(jsi::Runtime &runtime) const;
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/*
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* Releases the instance handler by nulling a strong reference to it.
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*/
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void release(jsi::Runtime &runtime) const;
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/*
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* Creates and returns the `instanceHandle`.
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* Returns `null` if the `instanceHandle` is not retained at this moment.
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*/
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jsi::Value getInstanceHandle(jsi::Runtime &runtime) const;
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/*
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* Deprecated. Do not use.
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*/
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Tag getTag() const;
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private:
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mutable bool enabled_{false}; // Protected by `EventEmitter::DispatchMutex()`.
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mutable jsi::WeakObject weakInstanceHandle_; // Protected by `jsi::Runtime &`.
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mutable jsi::Value strongInstanceHandle_; // Protected by `jsi::Runtime &`.
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Tag tag_;
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};
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using SharedEventTarget = std::shared_ptr<const EventTarget>;
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} // namespace react
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} // namespace facebook
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