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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
152 lines
4.6 KiB
C++
152 lines
4.6 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 "ShadowViewMutation.h"
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#include <utility>
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namespace facebook {
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namespace react {
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ShadowViewMutation ShadowViewMutation::CreateMutation(ShadowView shadowView) {
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return {
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/* .type = */ Create,
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/* .parentShadowView = */ {},
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/* .oldChildShadowView = */ {},
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/* .newChildShadowView = */ shadowView,
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/* .index = */ -1,
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};
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}
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ShadowViewMutation ShadowViewMutation::DeleteMutation(ShadowView shadowView) {
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return {
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/* .type = */ Delete,
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/* .parentShadowView = */ {},
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/* .oldChildShadowView = */ shadowView,
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/* .newChildShadowView = */ {},
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/* .index = */ -1,
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};
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}
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ShadowViewMutation ShadowViewMutation::InsertMutation(
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ShadowView parentShadowView,
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ShadowView childShadowView,
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int index) {
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return {
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/* .type = */ Insert,
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/* .parentShadowView = */ parentShadowView,
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/* .oldChildShadowView = */ {},
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/* .newChildShadowView = */ childShadowView,
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/* .index = */ index,
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};
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}
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ShadowViewMutation ShadowViewMutation::RemoveMutation(
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ShadowView parentShadowView,
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ShadowView childShadowView,
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int index) {
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return {
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/* .type = */ Remove,
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/* .parentShadowView = */ parentShadowView,
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/* .oldChildShadowView = */ childShadowView,
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/* .newChildShadowView = */ {},
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/* .index = */ index,
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};
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}
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ShadowViewMutation ShadowViewMutation::UpdateMutation(
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ShadowView oldChildShadowView,
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ShadowView newChildShadowView) {
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return {
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/* .type = */ Update,
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/* .parentShadowView = */ {},
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/* .oldChildShadowView = */ oldChildShadowView,
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/* .newChildShadowView = */ newChildShadowView,
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/* .index = */ -1,
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};
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}
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bool ShadowViewMutation::mutatedViewIsVirtual() const {
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bool viewIsVirtual = false;
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#ifdef ANDROID
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// Explanation: Even for non-virtual views,
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// for "Insert" mutations, oldChildShadowView is always empty.
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// for "Remove" mutations, newChildShadowView is always empty.
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// Thus, to see if a view is virtual, we need to always check both the old and
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// new View.
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viewIsVirtual = newChildShadowView.layoutMetrics == EmptyLayoutMetrics &&
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oldChildShadowView.layoutMetrics == EmptyLayoutMetrics;
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#endif
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return viewIsVirtual;
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}
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ShadowViewMutation::ShadowViewMutation(
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Type type,
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ShadowView parentShadowView,
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ShadowView oldChildShadowView,
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ShadowView newChildShadowView,
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int index)
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: type(type),
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parentShadowView(std::move(parentShadowView)),
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oldChildShadowView(std::move(oldChildShadowView)),
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newChildShadowView(std::move(newChildShadowView)),
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index(index) {}
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#if RN_DEBUG_STRING_CONVERTIBLE
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std::string getDebugName(ShadowViewMutation const &mutation) {
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switch (mutation.type) {
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case ShadowViewMutation::Create:
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return "Create";
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case ShadowViewMutation::Delete:
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return "Delete";
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case ShadowViewMutation::Insert:
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return "Insert";
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case ShadowViewMutation::Remove:
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return "Remove";
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case ShadowViewMutation::Update:
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return "Update";
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}
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}
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std::vector<DebugStringConvertibleObject> getDebugProps(
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ShadowViewMutation const &mutation,
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DebugStringConvertibleOptions options) {
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return {
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mutation.oldChildShadowView.componentHandle
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? DebugStringConvertibleObject{"oldChild",
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getDebugDescription(
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mutation.oldChildShadowView,
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options)}
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: DebugStringConvertibleObject{},
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mutation.newChildShadowView.componentHandle
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? DebugStringConvertibleObject{"newChild",
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getDebugDescription(
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mutation.newChildShadowView,
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options)}
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: DebugStringConvertibleObject{},
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mutation.parentShadowView.componentHandle
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? DebugStringConvertibleObject{"parent",
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getDebugDescription(
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mutation.parentShadowView,
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options)}
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: DebugStringConvertibleObject{},
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mutation.index != -1
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? DebugStringConvertibleObject{"index",
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getDebugDescription(
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mutation.index, options)}
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: DebugStringConvertibleObject{},
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};
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}
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#endif
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} // namespace react
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} // namespace facebook
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