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
71 lines
2.1 KiB
C++
71 lines
2.1 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 "ComponentBuilder.h"
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#include <utility>
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namespace facebook {
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namespace react {
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ComponentBuilder::ComponentBuilder(
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ComponentDescriptorRegistry::Shared componentDescriptorRegistry)
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: componentDescriptorRegistry_(std::move(componentDescriptorRegistry)){};
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ShadowNode::Unshared ComponentBuilder::build(
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ElementFragment const &elementFragment) const {
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auto &componentDescriptor =
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componentDescriptorRegistry_->at(elementFragment.componentHandle);
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auto children = ShadowNode::ListOfShared{};
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children.reserve(elementFragment.children.size());
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for (auto const &childFragment : elementFragment.children) {
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children.push_back(build(childFragment));
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}
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auto family = componentDescriptor.createFamily(
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ShadowNodeFamilyFragment{
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elementFragment.tag, elementFragment.surfaceId, nullptr},
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nullptr);
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auto state = componentDescriptor.createInitialState(
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ShadowNodeFragment{elementFragment.props}, family);
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auto constShadowNode = componentDescriptor.createShadowNode(
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ShadowNodeFragment{
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elementFragment.props,
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std::make_shared<ShadowNode::ListOfShared const>(children),
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state},
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family);
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if (elementFragment.stateCallback) {
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auto newState = componentDescriptor.createState(
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*family, elementFragment.stateCallback());
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constShadowNode = componentDescriptor.cloneShadowNode(
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*constShadowNode,
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ShadowNodeFragment{
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ShadowNodeFragment::propsPlaceholder(),
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ShadowNodeFragment::childrenPlaceholder(),
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newState});
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}
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auto shadowNode = std::const_pointer_cast<ShadowNode>(constShadowNode);
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if (elementFragment.referenceCallback) {
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elementFragment.referenceCallback(shadowNode);
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}
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if (elementFragment.finalizeCallback) {
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elementFragment.finalizeCallback(*shadowNode);
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}
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return shadowNode;
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}
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} // namespace react
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} // namespace facebook
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