kotlin - 如何获取/放置 Kotlin 内部 map 或 map

Question

有人知道我如何在Kotlin中“获取/放置”内部 map 吗？

var bookDetailsMap: MutableMap<Long, MutableMap<Long, Book>> = mutableMapOf()

我如何将下面的图书详细信息“放入”上方的 map 中

var books: MutableList<Book> = this.bookDao.findAll()

预计存储将像>

var bookDetailsMap: MutableMap<book.publisherId, MutableMap<book.bookId, Book>>

Answer 1

以这种方式成功实现:

放置示例:

var bookDetailsMap : Map<Long, Map<Long, BookDetail>> = hashMapOf()

this.bookDetailsMap = this.bookDao.findAll().groupBy { 
   it.publisherId
}.mapValues { 
   it.value.associateBy { it.bookId} 
}

获取示例:

var bookDetail : BookDetail = BookDetail ()

if (this.bookDetailsMap .containsKey(this.publisherId)) {
    bookDetail = this.bookDetailsMap [this.publisherId]!![this.bookId]!!
}