mirror of
https://github.com/facebook/react-native.git
synced 2025-11-01 09:14:26 +00:00
Samuel Susla
5fa6c5a941
Summary: changelog: [internal] You can read more about this rule on https://clang.llvm.org/extra/clang-tidy/checks/modernize-pass-by-value.html # Isn't it wasteful to copy? Isn't reference more efficient? This rule of thumb is no longer true since C++11 with move semantics. Let's look at some examples. # Option one ``` class TextHolder { public: TextBox(std::string const &text) : text_(text) {} private: std::string text_; }; ``` By using reference here, we prevent the caller from using rvalue to and avoiding copy. Regardless of what the caller passes in, copy always happens. # Option two ``` class TextHolder { public: TextBox(std::string const &text) : text_(text) {} TextBox(std::string &&text) : text_(std::move(text)) {} private: std::string text_; }; ``` Here, we provide two constructors, one for const reference and one for rvalue reference. This gives the caller option to avoid copy. But now we have two constructors, which is not ideal. # Option three (what we do in this diff) ``` class TextHolder { public: TextBox(std::string text) : text_(std::move(text)) {} private: std::string text_; }; ``` Here, the caller has option to avoid copy and we only have single constructor. Reviewed By: fkgozali, JoshuaGross Differential Revision: D33276841 fbshipit-source-id: 619d5123d2e28937b22874650366629f24f20a63
101 lines
2.7 KiB
C++
101 lines
2.7 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 <react/renderer/imagemanager/ImageResponse.h>
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#include <react/renderer/imagemanager/ImageResponseObserver.h>
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#include <react/renderer/imagemanager/ImageResponseObserverCoordinator.h>
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#include <react/renderer/imagemanager/ImageTelemetry.h>
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#include <react/renderer/imagemanager/primitives.h>
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namespace facebook {
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namespace react {
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/*
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* Represents ongoing request for an image resource.
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* The separate object must be constructed for every single separate
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* image request. The object cannot be copied because it would make managing of
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* event listeners hard and inefficient; the object can be moved though.
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* Destroy to cancel the underlying request.
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*/
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class ImageRequest final {
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public:
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/*
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* The default constructor
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*/
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ImageRequest(
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ImageSource imageSource,
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std::shared_ptr<const ImageTelemetry> telemetry);
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/*
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* The move constructor.
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*/
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ImageRequest(ImageRequest &&other) noexcept;
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/*
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* `ImageRequest` does not support copying by design.
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*/
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ImageRequest(const ImageRequest &other) = delete;
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~ImageRequest();
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/**
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* Set cancelation function.
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*/
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void setCancelationFunction(std::function<void(void)> cancelationFunction);
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/*
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* Returns the Image Source associated with the request.
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*/
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const ImageSource &getImageSource() const;
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/*
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* Returns stored observer coordinator as a shared pointer.
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* Retain this *or* `ImageRequest` to ensure a correct lifetime of the object.
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*/
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const std::shared_ptr<const ImageResponseObserverCoordinator>
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&getSharedObserverCoordinator() const;
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/*
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* Returns stored observer coordinator as a reference.
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* Use this if a correct lifetime of the object is ensured in some other way
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* (e.g. by retaining an `ImageRequest`).
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*/
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const ImageResponseObserverCoordinator &getObserverCoordinator() const;
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/*
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* Returns stored image telemetry object as a shared pointer.
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* Retain this *or* `ImageRequest` to ensure a correct lifetime of the object.
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*/
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const std::shared_ptr<const ImageTelemetry> &getSharedTelemetry() const;
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private:
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/*
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* Image source associated with the request.
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*/
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ImageSource imageSource_;
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/*
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* Image telemetry associated with the request.
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*/
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std::shared_ptr<const ImageTelemetry> telemetry_{};
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/*
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* Event coordinator associated with the reqest.
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*/
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std::shared_ptr<const ImageResponseObserverCoordinator> coordinator_{};
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/*
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* Function we can call to cancel image request (see destructor).
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*/
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std::function<void(void)> cancelRequest_;
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};
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} // namespace react
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} // namespace facebook
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