CODEWITHSUNDEEP
mongodbscala
summerNight
summerNight

Reputation: 1496

Scala filter a list based on a max value

I have the following MAP:

[
  { "animal": "dog", "age": 1},
  { "animal": "dog", "age": 2},
  { "animal": "dog", "age": 3},
  { "animal": "cat", "age": 1},
  { "animal": "cat", "age": 4},
  { "animal": "rabbit", "age": 9}
]

How do I return a result so that I get both dogs, cats and rabbits with the max age. Example:

[
    { "animal": "dog", "age": 3},    # oldest dog in DB
    { "animal": "cat", "age": 4},    # oldest cat in DB
    { "animal": "rabbit", "age": 9}  # oldest rabbit in DB

]

I am trying to get this using two scala .map() aggregation but no success so far.

Upvotes: 2

Views: 2200

Answers (1)

Alvaro Carrasco
Alvaro Carrasco

Reputation: 6182

Assuming a case class like case class Pet(animal: String, age: Int):

list.groupBy(_.animal).values.map(_.maxBy(_.age)).toList

For List[BSONDocument], same concept:

list.groupBy(_.getAs[String]("animal")).values.map(_.maxBy(_.getAs[Int]("age"))).toList

Upvotes: 4

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