Combining results topic

Combine several query results into one: (a, b).combine(...) over a record of results, combine over a list, optional() for sources a combination can do without, and CombineMemo to keep the combined value stable.

Classes

CombinedData<T>

Every source has data; data is what the combiner made of it.

CombinedError<T>

A source failed and has no data to fall back on. retry() refetches the failed sources.

CombinedPending<T>

At least one source has nothing to show yet, and none has failed outright.

CombinedResult<T>

What several QueryResults amount to together: nothing to show yet (CombinedPending), a source that failed with nothing to show (CombinedError), or every source's data run through the combiner (CombinedData).

CombineMemo<T>

Remembers the last combination, so a combiner runs only when a source's data really changed and an equal result keeps its instance.

Extensions

CombineQueryResultList on List<QueryResult<T>>

combine over a list of results of one type — a QueriesObserver's results, say, one per item of a dynamic list — by the same rules as a record of them, and combineWith for that list plus one more source of another type.

CombineQueryResults2 on (QueryResult<A>, QueryResult<B>)

combine over a record of two results: runs the combiner once both have data, by the rules on CombinedResult.

CombineQueryResults3 on (QueryResult<A>, QueryResult<B>, QueryResult<C>)

combine over a record of three results: runs the combiner once all three have data, by the rules on CombinedResult.

CombineQueryResults4 on (QueryResult<A>, QueryResult<B>, QueryResult<C>, QueryResult<D>)

combine over a record of four results: runs the combiner once all four have data, by the rules on CombinedResult.

CombineQueryResults5 on (QueryResult<A>, QueryResult<B>, QueryResult<C>, QueryResult<D>, QueryResult<E>)

combine over a record of five results: runs the combiner once all five have data, by the rules on CombinedResult.

CombineQueryResults6 on (QueryResult<A>, QueryResult<B>, QueryResult<C>, QueryResult<D>, QueryResult<E>, QueryResult<F>)

combine over a record of six results: runs the combiner once all six have data, by the rules on CombinedResult. Past six, combine a list of what the sources have in common — <QueryResult<Object?>>[...] at worst — and cast in the combiner; a CombinedResult is not a source, so two combinations cannot be combined.

OptionalQueryResult on QueryResult<T>

Marks a source a combination can do without — see optional.