Android Development with Kotlin

No method overriding

When there is a member function and an extension function with the same name and parameters, the member function always wins. Here is an example:

    class A { 
        fun foo() { 
            println("foo from A") 
        } 
    } 
 
    fun A.foo() { 
        println("foo from Extension") 
    } 
 
    A().foo() // Prints: foo from A 

This is always true. Even methods from a superclass win with extension functions:

    open class A { 
        fun foo() { 
            println("foo from A") 
        } 
    } 
 
    class B: A() 
 
    fun B.foo() { 
        println("foo from Extension") 
    } 
 
    A().foo() // foo from A 

The point is that the extension function is not allowed to modify the behavior of a real object. We can only add extra functionalities. This keeps us secure, because we know that no one will change the behavior of objects that we are ...