kotlin - 给定列表列表，如何获取单个唯一的项目列表

Question

给定以下模型:

class Participant {
   var email = ""
}

class Reservation {
   var participants = ArrayList<Participant>()
}

val reservations = ArrayList<Reservation>()

我如何以 reservations获得唯一的电子邮件列表，但前提是该电子邮件不为空白？

Answer 1

你有没有尝试过:

reservations.flatMap { reservation -> reservation.participants }
            .distinctBy { participant -> participant.email }
            .map { participant -> participant.email }
            .filter { email -> email.isNotBlank() } 

？