Kotlin properties and encapsulation

[jmfayard]

Hello @Zhuinden
I have finished reviewing your guide.
Nice job, this will be useful to lots of people! 👍

There is one big thing I rewrote that you probably will want to review: Kotlin properties.
They look simple so people don't pay attention, but I find them one of the most useful and under-hyped aspects of Kotlin.

https://github.com/Zhuinden/guide-to-kotlin/wiki/4.)-The-Tricky-Stuff#kotlin-properties-and-encapsulation
(Not sure if they should stay in the "tricky stuff" page!)

Another concern I have is that by creating, moving or renaming some paragraphs, I have probably broken some of the links in the README.

[Zhuinden]

Thanks, I tweaked it a bit but overall it's good.

The response: List<T> by data was a bit of a hack, but I guess it can make sense. 🤔

I still think delegates are a bit tricky, I have for example never seen a lazy and vetoable at the same time. I'm actually not even sure if it is possible.

[jmfayard]

@Zhuinden

In general, I think you shouldn't combine properties: you should write your own function that generates a Read(Only|Write)Property or Lazy<T> that has the two features you are interested in.

class MainActivity : AppCompatActivity(), HasFindViewById {
  val username by editText(R.id.username)
  val password by editText(R.id.password)

 fun onCreate() { ... } 

}

implemented by

fun HasFindViewById.editText(@IdRes editText: Int): Lazy<EditText> =
  lazy(LazyThreadSafetyMode.NONE) {
    findViewById<EditText>(editText)
  }

fun HasFindViewById.textView(@IdRes editText: Int) : Lazy<TextView>
    // same implementation

// because I don't want to write the same functions for ViewGroup and Fragment and Activity...
interface HasFindViewById {
  fun <T : View?> findViewById(id: Int): T
}

On the other hand, this a very common use case and it is optimized by a special tool (android kotlin extensions) so I would classify that as a overuse of the pattern.