/** * `Transaction` creates a black box that is able to wrap any method such that * certain invariants are maintained before and after the method is invoked * (Even if an exception is thrown while invoking the wrapped method). Whoever * instantiates a transaction can provide enforcers of the invariants at * creation time. The `Transaction` class itself will supply one additional * automatic invariant for you - the invariant that any transaction instance * should not be run while it is already being run. You would typically create a * single instance of a `Transaction` for reuse multiple times, that potentially * is used to wrap several different methods. Wrappers are extremely simple - * they only require implementing two methods. * * <pre> * wrappers (injected at creation time) * + + * | | * +-----------------|--------|--------------+ * | v | | * | +---------------+ | | * | +--| wrapper1 |---|----+ | * | | +---------------+ v | | * | | +-------------+ | | * | | +----| wrapper2 |--------+ | * | | | +-------------+ | | | * | | | | | | * | v v v v | wrapper * | +---+ +---+ +---------+ +---+ +---+ | invariants * perform(anyMethod) | | | | | | | | | | | | maintained * +----------------->|-|---|-|---|-->|anyMethod|---|---|-|---|-|--------> * | | | | | | | | | | | | * | | | | | | | | | | | | * | | | | | | | | | | | | * | +---+ +---+ +---------+ +---+ +---+ | * | initialize close | * +-----------------------------------------+ * </pre> * * Use cases: * - Preserving the input selection ranges before/after reconciliation. * Restoring selection even in the event of an unexpected error. * - Deactivating events while rearranging the DOM, preventing blurs/focuses, * while guaranteeing that afterwards, the event system is reactivated. * - Flushing a queue of collected DOM mutations to the main UI thread after a * reconciliation takes place in a worker thread. * - Invoking any collected `componentDidUpdate` callbacks after rendering new * content. * - (Future use case): Wrapping particular flushes of the `ReactWorker` queue * to preserve the `scrollTop` (an automatic scroll aware DOM). * - (Future use case): Layout calculations before and after DOM updates. * * Transactional plugin API: * - A module that has an `initialize` method that returns any precomputation. * - and a `close` method that accepts the precomputation. `close` is invoked * when the wrapped process is completed, or has failed. * * @param {Array<TransactionalWrapper>} transactionWrapper Wrapper modules * that implement `initialize` and `close`. * @return {Transaction} Single transaction for reuse in thread. * * @class Transaction */
简单的说就是,加入到某个transaction中之后,这个transaction会有前置和后置的wrapper,不如停止event,还原selection之类的。