I don't understand why is possible to write a function outside a class in Kotlin ? Is that a good practice ?
For example, it's possible in Kotlin to write a function outside my MainActivity class :
fun hello(){}
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
hello()
}
}
In Java, this is impossible! That's not how an object-oriented language works normally, right?
In the documentation, they talk of Local Functions for the classic function and Member Functions for the function defined inside a class or object but they don't explain when it's better to use one or the other.
In Java, this is impossible! That's not how an object-oriented language works normally, right?
Just stop for a second and reconsider the nature of java's static method. A class is supposed to be a blueprint for objects, describe their behavior and state. But you can call a static method without creating any instances.
How does that fit into the object-oriented picture? How does a static method "belong" to the class it's declared in?
Actually static methods are a hack in Java, they pollute and misuse the OOP notion of a class. But you got used to them over the years so you don't feel that anymore.
Conceptually, a static method is a top-level function and Java uses the name of its declaring class as its namespace. In contrast to that, Kotlin allows you to declare top-level functions without misusing the class for namespacing.