Easy idiomatic way to define Ordering for a simple case class

Question

I have a list of simple scala case class instances and I want to print them in predictable, lexicographical order using list.sorted, but receive \"No implicit O

Answer 1

To summarize, there are three ways to do this:

1. For one-off sorting use .sortBy method, as @Shadowlands have showed
2. For reusing of sorting extend case class with Ordered trait, as @Keith said.

3. Define a custom ordering. The benefit of this solution is that you can reuse orderings and have multiple ways to sort instances of the same class:

   case class A(tag:String, load:Int)
   
   object A {
     val lexicographicalOrdering = Ordering.by { foo: A => 
       foo.tag 
     }
   
     val loadOrdering = Ordering.by { foo: A => 
       foo.load 
     }
   }
   
   implicit val ord = A.lexicographicalOrdering 
   val l = List(A("words",1), A("article",2), A("lines",3)).sorted
   // List(A(article,2), A(lines,3), A(words,1))
   
   // now in some other scope
   implicit val ord = A.loadOrdering
   val l = List(A("words",1), A("article",2), A("lines",3)).sorted
   // List(A(words,1), A(article,2), A(lines,3))
   

Answering your question Is there any standard function included into the Scala that can do magic like List((2,1),(1,2)).sorted

There is a set of predefined orderings, e.g. for String, tuples up to 9 arity and so on.

No such thing exists for case classes, since it is not easy thing to roll off, given that field names are not known a-priori (at least without macros magic) and you can't access case class fields in a way other than by name/using product iterator.