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
54 lines
1.2 KiB
C++
54 lines
1.2 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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#include "State.h"
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#include <react/renderer/core/ShadowNode.h>
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#include <react/renderer/core/ShadowNodeFragment.h>
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#include <react/renderer/core/State.h>
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#include <react/renderer/core/StateData.h>
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#include <utility>
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namespace facebook {
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namespace react {
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State::State(StateData::Shared data, State const &state)
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: family_(state.family_),
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data_(std::move(data)),
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revision_(state.revision_ + 1){};
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State::State(StateData::Shared data, ShadowNodeFamily::Shared const &family)
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: family_(family),
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data_(std::move(data)),
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revision_{State::initialRevisionValue} {};
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State::Shared State::getMostRecentState() const {
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auto family = family_.lock();
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if (!family) {
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return {};
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}
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return family->getMostRecentState();
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}
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State::Shared State::getMostRecentStateIfObsolete() const {
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auto family = family_.lock();
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if (!family) {
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return {};
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}
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return family->getMostRecentStateIfObsolete(*this);
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}
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size_t State::getRevision() const {
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return revision_;
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}
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} // namespace react
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} // namespace facebook
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