Hands-On Design Patterns with Kotlin

Creating an email – second attempt

Let's try a fluent setter approach instead. We'll have only mandatory fields in our constructor, and all others will become setters, so the creation of a new email would look something like this:

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

That's a lot nicer for many reasons:

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

Let's see one way of implementing this approach. There are other convenient ways to do it, which we'll discuss in Chapter 10, Idioms and Anti-Patterns:

data class ...