List of Lists GroupBy

Question

我怎样才能成功地做这样的事情呢？

trips.groupBy { Passenger::name if Passenger in it.passengers} 

我想对List<Passengers>为[PassengerA: List<Trips>, PassengerB:...]的List<Trips>重新排序

Answer 1

如果我没理解错你的问题，这可能是一种你想做的事情：

val passengersToTrips = trips
    .flatMap { trip ->
        // Associate every passenger in a trip to the trip: this results in a List<Pair<Passenger, Trip>>
        trip.passengers.map { passenger -> passenger to trip }
    }
    .groupBy(
        // Group using the passenger as key (use passenger.name in case the name should be the key)
        keySelector = { (passenger, _) -> passenger },
        // Extracting only the trip from the pair to transform from List<Pair<Passenger, Trip> into List<Trip> 
        valueTransform = { (_, trip) -> trip }
    )