I think Stack singleton (if it stands alone) or Stack companion (if it comes with a class) is the best way to name object Stack. The Scala Language Reference calls them modules. But modules have by now been too much associated with run-time entities (as in OSGI) to be comfortable with that.
The reason why case class companion objects implement FunctionN is that before, case classes generated a class and a factory method, not a companion object. When we added extractors to Scala it made more sense to turn the factory method into a full companion object with apply and unapply methods. But then, since the factory … Read more
please see this go to link class MainApplication : Application() { init { instance = this } companion object { private var instance: MainApplication? = null fun applicationContext() : Context { return instance!!.applicationContext } } override fun onCreate() { super.onCreate() // initialize for any // Use ApplicationContext. // example: SharedPreferences etc… val context: Context = … Read more
I don’t think there’s anything deeper going on than what you have originally said: it’s just syntactic sugar whereby the compiler converts f(a) into f.apply(a) as a special syntax case. This might seem like a specific rule, but only a few of these (for example, with update) allows for DSL-like constructs and libraries.
There are two different types of object uses, expression and declaration. Object Expression An object expression can be used when a class needs slight modification, but it’s not necessary to create an entirely new subclass for it. Anonymous inner classes are a good example of this. button.setOnClickListener(object: View.OnClickListener() { override fun onClick(view: View) { // … Read more
The companion object basically provides a place where one can put “static-like” methods. Furthermore, a companion object, or companion module, has full access to the class members, including private ones. Companion objects are great for encapsulating things like factory methods. Instead of having to have, for example, Foo and FooFactory everywhere, you can have a … Read more