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API > @ngrx/effects ofType 有大用
ofType
'ofType' filters an Observable of Actions into an observable of the actions whose type strings are passed to it.
ofType<E extends Extract<U, {
type: T1;
}>, AC extends ActionCreator<string, Creator>, T1 extends string | AC, U extends Action = Action, V = T1>()Parameters
There are no parameters.
Description
For example, if actions has type Actions<AdditionAction|SubstractionAction>, and the type of the Addition action is add, then actions.pipe(ofType('add')) returns an Observable<AdditionAction>.
Properly typing this function is hard and requires some advanced TS tricks below.
Type narrowing automatically works, as long as your actions object starts with a Actions<SomeUnionOfActions> instead of generic Actions.
For backwards compatibility, when one passes a single type argument ofType<T>('something') the result is an Observable<T>. Note, that T completely overrides any possible inference from 'something'.
Unfortunately, for unknown 'actions: Actions' these types will produce 'Observableactions.ofType<AdditionAction>('add').
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Fallback for more than 5 arguments. There is no inference, so the return type is the same as the input - Observable Parameters
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We provide a type parameter, even though TS will not infer it from the arguments, to preserve backwards compatibility with old versions of ngrx. | ||||||||||
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