Book Image

Kotlin Programming Cookbook

By : Aanand Shekhar Roy, Rashi Karanpuria
Book Image

Kotlin Programming Cookbook

By: Aanand Shekhar Roy, Rashi Karanpuria

Overview of this book

The Android team has announced first-class support for Kotlin 1.1. This acts as an added boost to the language and more and more developers are now looking at Kotlin for their application development. This recipe-based book will be your guide to learning the Kotlin programming language. The recipes in this book build from simple language concepts to more complex applications of the language. After the fundamentals of the language, you will learn how to apply the object-oriented programming features of Kotlin 1.1. Programming with Lambdas will show you how to use the functional power of Kotlin. This book has recipes that will get you started with Android programming with Kotlin 1.1, providing quick solutions to common problems encountered during Android app development. You will also be taken through recipes that will teach you microservice and concurrent programming with Kotlin. Going forward, you will learn to test and secure your applications with Kotlin. Finally, this book supplies recipes that will help you migrate your Java code to Kotlin and will help ensure that it's interoperable with Java.
Table of Contents (21 chapters)
Title Page
Copyright and Credits
Packt Upsell
Contributors
Preface
Index

Disambiguating using the "as" keyword to locally rename the clashing entity


Disambiguation refers to the removal of ambiguity by making something clear. Importing a library or a class in code is a daily routine of a programmer. It’s pretty easy to import files into the code in every language, thanks to the great code editors nowadays.

However, what happens if you try to import two classes into a file? Though you should always try to have different names for different classes, sometimes it’s unavoidable. For example, in the case of different libraries having the same name for their classes. In Java, there is a workaround; you have to use the full qualifier, which looks something like this:

class X {
   com.very.very.long.prefix.bar.Foo a;
   org.other.very.very.long.prefix.baz.Foo b;
   ...
}

Dirty, isn’t it? Now, let’s see how Kotlin addresses it gracefully.

Getting ready

Ensure that you have a code editor on which you can write and run the code. To test things out, you can create two classes with the same name but under different packages. Refer to the example here:

How to do it...

In the following steps and examples, we will see how we can disambiguate classes of the similar name using Kotlin's keyword.

  1. In Kotlin, you can disambiguate using the as keyword to locally rename the clashing entity. So in Kotlin, it will look as shown:
import foo.Bar // Bar is accessible
import bar.Bar as bBar // bBar stands for 'bar.Bar'
  1. Then, access their methods like this:
Bar.methodOfFooBar()
bBar.methodOfBarBar()

For example, let's see the use of the as keyword to disambiguate two classes having the same name (SomeClass.kt), but in different packages:

SameClass.kt (packageA)

package packageA
class SameClass {
  companion object {
      fun methodA(){
          println("Method a")
      }
  }
}

SameClass.kt (packageB)

package packageB
class SameClass {
  companion object {
      fun methodB(){
          println("Method b")
      }
  }
}

HelloWorld.kt is the class that uses classes with similar names:

import packageA.SameClass as anotherSameClass
import packageB.SameClass
fun main(args: Array<String>) {
   anotherSameClass.methodA()
   SameClass.methodB()

}