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58 lines
1.6 KiB
C
58 lines
1.6 KiB
C
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/**
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* Copyright (c) 2015-present, Facebook, Inc.
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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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namespace facebook {
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namespace react {
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/*
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* Represents something which can be *sealed* (imperatively marked as immutable).
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*
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* Why do we need this? In Fabric, some objects are semi-immutable
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* even if they explicitly marked as `const`. It means that in some special
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* cases those objects can be const-cast-away and then mutated. That comes from
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* the fact that we share some object's life-cycle responsibilities with React
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* and the immutability is guaranteed by some logic splitted between native and
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* JavaScript worlds (which makes impossible to fully use immutability
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* enforcement at a language level).
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* To detect possible errors as early as possible we additionally mark objects
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* as *sealed* after some stage and then enforce this at run-time.
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*
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* How to use:
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* 1. Inherit your class from `Sealable`.
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* 2. Call `ensureUnsealed()` from all non-const methods.
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* 3. Call `seal()` at some point from which any modifications
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* must be prevented.
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*/
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class Sealable {
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public:
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/*
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* Seals the object. This operation is irreversible;
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* the object cannot be "unsealed" after being sealing.
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*/
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void seal() const;
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/*
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* Returns if the object already sealed or not.
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*/
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bool getSealed() const;
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protected:
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/*
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* Throws an exception if the object is sealed.
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* Call this from all non-`const` methods.
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*/
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void ensureUnsealed() const;
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private:
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mutable bool sealed_ {false};
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};
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} // namespace react
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} // namespace facebook
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