65 lines
2.9 KiB
Objective-C
65 lines
2.9 KiB
Objective-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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#import <UIKit/UIKit.h>
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#import <react/mounting/MountingTransactionMetadata.h>
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NS_ASSUME_NONNULL_BEGIN
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/*
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* # Achtung!
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* Remember, with great power comes great responsibility.
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* Observers of this protocol are being called several times on every single mount transaction. Any thoughtless or
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* suboptimal implementation of this protocol will slow down the whole app. Please, be responsible.
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*
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* # Usecases
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* React Native platform-specific mounting layer has limitations when it comes to notifying view components about
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* (coming or just happened) changes in the view tree. Implementing that generically for all components would make
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* everything way to slow. For instance, the mounting layer does not have dedicated APIs to notify some component that:
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* - Some ancestor of the component was reparented;
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* - Some descendant of the component was added, removed or reparented;
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* - Some ancestor of the component got new layout metrics (which might affect the absolute position of the component);
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* - The transaction which affected the component's children just finished.
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*
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* If some very specific component (e.g. a performance logger) needs to handle some of the similar use-cases, it might
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* rely on this protocol.
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*
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* # How to use
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* - Declare conformance to this protocol for the ComponentView class.
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* - Implement methods *only* suitable for a particular use case. Do not implement all methods if it is not strictly
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* required.
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* - Alternatively, an observer can be registered explicitly via `RCTSurface`.
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*
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* # Implementation details
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* The framework checks all registered view classes for conformance to the protocol and for a set of implemented
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* methods, then it stores this information for future use. When a view got created, the framework checks the info
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* associated with the class and adds the view object to the list of listeners of the particular events (if needed).
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* When a view got destroyed, the framework removes the view from suitable collections.
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*/
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@protocol RCTMountingTransactionObserving <NSObject>
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@optional
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/*
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* Called right before the fist mutation instruction is executed.
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* Is not being called for a component view which is being mounted as part of the transaction (because the view is not
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* registered as an observer yet).
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*/
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- (void)mountingTransactionWillMountWithMetadata:(facebook::react::MountingTransactionMetadata const &)metadata;
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/*
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* Called right after the last mutation instruction is executed.
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* Is not being called for a component view which was being unmounted as part of the transaction (because the view is
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* not registered as an observer already).
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*/
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- (void)mountingTransactionDidMountWithMetadata:(facebook::react::MountingTransactionMetadata const &)metadata;
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@end
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NS_ASSUME_NONNULL_END
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