Scala's naming convention for traits

Question

Suppose I have a trait in Scala

trait Connection {    def init(name: String)   def dispose } 

And I want to create a class which implements it. But I want to name it as Connection also:

class Connection extends Connection {   // ....  } 

It's not going to work. Of course, I could name trait something differently, but it turned out that the naming convention in Scala says that I should name trait as ordinary classes, meaning without any prefix, which I would use in C# (IConnection where IConnection would be the interface).

And in this particular case the name of Connection for the class and the trait is more suitable.

Or did I miss something in Scala's naming convention?

Answer 1

The fact that you are extracting a general API into a Connection trait itself implies that it'll have multiple specific implementations. Those implementations will of course be related to some more specific entities, e.g. a MySQL or an H2 database.

There are several approaches to your problem depending on the chosen architecture of your app:

1. If you keep the specific implementations in the same namespace you get:

   • myApp.Connection

   • myApp.MySqlConnection

   • myApp.H2Connection

2. But the above is actually discouraged due to redundancy in names (the *Connection part) and introduction of a new package is recommended, e.g.:

   • myApp.Connection

   • myApp.connections.MySql

   • myApp.connections.H2

   or

   • myApp.Connection

   • myApp.Connection.MySql

   • myApp.Connection.H2

   if you choose to place the specific implemntation in a companion object of Connection.

3. In more advanced approaches to architecture you will end up with specific implementations having private packages:

   • myApp.Connection

   • myApp.mySql.Connection

   • myApp.h2.Connection

   And even here although you have the Connection name clashing it's easily solvable due to types being located in different packages by using qualified references (myApp.Connection) or qualified imports:

   import myApp.{Connection => GeneralConnection} //or IConnection if you insist