Scala Tutorial

Welcome to the Scala Tutorials.  Scala is a modern multi-paradigm programming language designed to express common programming patterns in a concise, elegant, and type-safe way. Scala has been created by Martin Odersky and he released the first version in 2003

In addition to free Scala Tutorials, you can find interview questions, how to tutorials and issues and their resolutions of Scala.

Introduction

Scala is a programming language for general software applications. The design of Scala started in 2001, and the first public release was in 2004. The name Scala is a combination of the words “Scalable” and “Language,” which was chosen to indicate its design goal of growing with the demands of the user base. Many of the design decisions of Scala are inspired by perceived shortcomings of the Java language with Scala source code compiling to Java Byte Code, allowing it to run on a Java virtual machine. One of the biggest attractions of Scala is that it has full support for functional programming and has a very strong static type system. This allows for very concise code, requiring fewer lines of code to achieve the same functionality than many other languages, including Java.

Scala Features

Scala is both functional and object-oriented

- every value is an object

- every function is a value--including methods Scala is statically typed

-includes a local type inference system:

in Java 1.5: Pair p = new Pair<Integer, String>(1, "Scala");

in Scala:val p = new MyPair(1, "scala");

Supports lightweight syntax for anonymous functions, higher-order functions, nested functions, currying

ML-style pattern matching

Integration with XML

-Can write XML directly in Scala program

-Can convert XML DTD into Scala class definitions

Support for regular expression patterns

Allows defining new control structures without using macros, and while maintaining static typing

Any function can be used as an infix or postfix operator

Can define methods named +, <= or ::

Scala object system

-Class-based

-Single inheritance

-Can define singleton objects easily

-Subtyping is nominal

-Traits, compound types, and views allow for more flexibility

Scala Operators

An operator is a symbol that tells the compiler to perform specific mathematical or logical manipulations. Scala is rich in built-in operators and provides following type of operators:

-Arithmetic Operators

-Relational Operators

-Logical Operators

-Bitwise Operators

-Assignment Operators

Scala Collections

Collections are containers of things. Those containers can be sequenced, linear sets of items like List, Tuple, Option, Map, etc. The collections may have an arbitrary number of elements or be bounded to zero or one element (e.g., Option).

Basic Data Structures

-Lists

-Sets

-Tuple

-Maps

-Option

Functional Combinators

-map

-foreach

-filter

-zip

-partition

-find

-drop and dropWhile

-foldRight and foldLeft

-flatten

-flatMap

-Generalized functional combinators

-Map

Scala Data Types

Scala Configuration

The separation of configuration from code is a good practice that makes our system customisable as we can load different configurations according to the environment we are running it in. In this article we will describe different approaches to load configurations in Scala and how they can be combined together: loading configurations from a file, from command line parameters or from environment variables.

Configurations from a file

Let’s start with the basic case scenario: given a file, we want to read it and parse its values to use them in our code.

First, we need to define our configuration file, let’s call itapplication.conf.

// application.conf
my {
     secret {
       value = "super-secret"
     }
}

// config-tutorial.scala
importcom.typesafe.config.ConfigFactory
valvalue =ConfigFactory.load().getString("my.secret.value")
println(s"My secret value is $value")

// application.conf
my {
     secret {
       value ="super-secret"
       value =${?VALUE}
     }
}

>> scala config-tutorial.scala 
My secret value is super-secret
>> scala config-tutorial.scala -Dmy.secret.value=another-secret
My secret value is another-secret

importscala.util.Properties
 defenvOrElseConfig(name:String):String ={
  Properties.envOrElse(
    name.toUpperCase.replaceAll("""\.""", "_"),
      config.getString(name)
      )
}   

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/ application.conf
my {
  secret {
   value ="super-secret"
   value =${?VALUE}
  }
}

The script can be used as following:
valmyConfig =newMyConfig()
valvalue =myConfig.envOrElseConfig("my.secret.value")
println(s"My secret value is $value")