Hands-On Design Patterns with Kotlin

Creating an email – the Kotlin way – second attempt

Let's try a fluent setter approach, instead. We'll have only mandatory fields in our constructor, and all of the others will become setters. So to create a new email, we no longer need to do the following:

   val mail = Mail("[e-mail]") 
   mail.title("Ping") 
   mail.cc(listOf<String>()) 

Instead, we will do the following:

Mail("[e-mail]").title("Ping").cc(listOf<String>())

Fluent setters allow us to chain one set call to another.

That's a lot nicer for a couple of reasons:

• The order of fields can now be arbitrary, unlike the order used with the constructor.
• It's clearer which field is being set; no more need for comments.
• Optional fields don't need to be set at all. As an ...