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Learning Scala Programming

You're reading from   Learning Scala Programming Object-oriented programming meets functional reactive to create Scalable and Concurrent programs

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Product type Paperback
Published in Jan 2018
Publisher Packt
ISBN-13 9781788392822
Length 426 pages
Edition 1st Edition
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Author (1):
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Vikash Sharma Vikash Sharma
Author Profile Icon Vikash Sharma
Vikash Sharma
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Table of Contents (16) Chapters Close

1. Getting Started with Scala Programming 2. Building Blocks of Scala FREE CHAPTER 3. Shaping our Scala Program 4. Giving Meaning to Programs with Functions 5. Getting Familiar with Scala Collections 6. Object-Oriented Scala Basics 7. Next Steps in Object-Oriented Scala 8. More on Functions 9. Using Powerful Functional Constructs 10. Advanced Functional Programming 11. Working with Implicits and Exceptions 12. Introduction to Akka 13. Concurrent Programming in Scala 14. Programming with Reactive Extensions 15. Testing in Scala 16. Other Books You May Enjoy

Looking for implicits


Your usual application Scala code might contain some constructs that import other classes and objects, or it might also inherit other classes. You write methods that expect types as parameters and also declare parameters. So when the Scala compiler looks for an implicit value, where should it start looking for such a value? The compiler starts to look for an implicit value according to the following criteria:

  • Defined in current scope
  • Explicitly imported
  • Imported using wildcards
  • Companion object of a type
  • Implicit scope of an argument's type
  • Implicit scope of type arguments
  • Outer objects for nested types

We know that if we define an implicit value in the current scope (block of code), it gets the highest precedence. Afterwards, you can also import it using an import statement, as shown in the following code:

import scala.concurrent.Future 
import scala.concurrent.ExecutionContext.Implicits.global 
 

object FuturesApp extends App { 
 
  val futureComp = Future { 
     1 + 1 ...
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