Sort collection by multiple fields in Kotlin

Question

Let s say I have a list of People which I need to sort by Age first and then by Name    Coming from a C -background  I can easily achieve this in said language by using LINQ   var list new List lt Person gt     list Add new Person 25   Tom     list Add new Person 25   Dave     list Add new Person 20   Kate     list Add new Person 20   Alice        will produce  Alice  Kate  Dave  Tom var sortedList list OrderBy person   gt  person Age  ThenBy person   gt  person Name  ToList       How does one accomplish this using Kotlin   This is what I tried  it s obviously wrong since the output of the first  sortedBy  clause gets overridden by the second one which results in a list sorted by Name only   val sortedList   ArrayList list sortedBy   it age   sortedBy   it name       wrong

User · Answer

Use sortedWith to sort a list with Comparator   You can then construct a comparator using several ways    compareBy  thenBy construct the comparator in a chain of calls   list sortedWith compareBy lt Person gt    it age   thenBy   it name   thenBy   it address     compareBy has an overload which takes multiple functions   list sortedWith compareBy   it age      it name      it address

User · Answer

sortedWith   compareBy  taking a vararg of lambdas  do the trick   val sortedList   list sortedWith compareBy   it age      it name       You can also use the somewhat more succinct callable reference syntax   val sortedList   list sortedWith compareBy Person  age  Person  name

[kotlin] Sort collection by multiple fields in Kotlin

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