mergeMap<R> method
For each value of this Observable, transform that value to a
higher-order observable with the provided project
function and merge
its emitted values. Subscribe to at most concurrent
sources.
Implementation
Observable<R> mergeMap<R>(
Map1<T, Observable<R>> project, {
int concurrent = maxInteger,
}) => MergeObservable<T, R>(this, project, concurrent);