mirror of
https://github.com/facebook/react-native.git
synced 2025-11-01 09:14:26 +00:00
Samuel SuslaandFacebook GitHub Bot
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
115 lines
3.0 KiB
C++
115 lines
3.0 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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#ifdef ANDROID
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#include <folly/dynamic.h>
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#include <react/renderer/mapbuffer/MapBuffer.h>
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#include <react/renderer/mapbuffer/MapBufferBuilder.h>
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#endif
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#include <react/renderer/core/ShadowNodeFamily.h>
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namespace facebook {
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namespace react {
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/*
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* An abstract interface of State.
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* State is used to control and continuously advance a single vision of some
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* state (arbitrary data) associated with a family of shadow nodes.
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*/
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class State {
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public:
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using Shared = std::shared_ptr<const State>;
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static size_t constexpr initialRevisionValue = 1;
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protected:
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/*
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* Constructors are protected to make calling them directly with
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* type-erasured arguments impossible.
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*/
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explicit State(StateData::Shared data, State const &state);
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explicit State(
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StateData::Shared data,
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ShadowNodeFamily::Shared const &family);
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public:
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virtual ~State() = default;
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/*
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* Returns a momentary value of the most recently committed state
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* associated with a family of nodes which this state belongs to.
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* Sequential calls might return different values.
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*/
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State::Shared getMostRecentState() const;
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/*
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* Returns the most recent state (same as `getMostRecentState()` method)
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* if this state is obsolete, otherwise returns `nullptr`.
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*/
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State::Shared getMostRecentStateIfObsolete() const;
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/*
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* Returns a revision number of the `State` object.
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* The number is being automatically assigned during the creation of `State`
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* objects.
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* Revision `0` represents a case when we don't have any info about state
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* object (actual State instances cannot have it).
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* Revision `1` represents a newly created initial state object.
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*/
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size_t getRevision() const;
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#ifdef ANDROID
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virtual folly::dynamic getDynamic() const = 0;
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virtual MapBuffer getMapBuffer() const = 0;
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virtual void updateState(folly::dynamic data) const = 0;
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#endif
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protected:
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friend class ShadowNodeFamily;
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friend class UIManager;
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/*
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* Returns a shared pointer to data.
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* To be used by `UIManager` only.
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*/
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StateData::Shared const &getDataPointer() const {
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return data_;
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}
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/*
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* A family of a node with this state is associated.
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* Must be a weak pointer to avoid retain cycle among `State`, `ShadowNode`,
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* and `ShadowNodeFamily` instances.
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*/
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ShadowNodeFamily::Weak family_;
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/*
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* Type-erasured pointer to arbitrary component-specific data held by the
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* `State`.
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*/
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StateData::Shared data_;
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/*
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* Indicates that the state was committed once and then was replaced by a
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* newer one.
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* To be used by `StateCoordinator` only.
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* Protected by mutex inside `StateCoordinator`.
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*/
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mutable bool isObsolete_{false};
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/*
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* Revision of the State object.
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*/
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size_t revision_;
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};
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} // namespace react
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} // namespace facebook
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