{"id":18090,"date":"2018-06-09T04:20:02","date_gmt":"2018-06-09T04:20:02","guid":{"rendered":"https:\/\/data-flair.training\/blogs\/?p=18090"},"modified":"2021-12-04T10:15:25","modified_gmt":"2021-12-04T04:45:25","slug":"scala-constructor","status":"publish","type":"post","link":"https:\/\/data-flair.training\/blogs\/scala-constructor\/","title":{"rendered":"Scala Constructor – 2 Popular Types of Constructors in Scala"},"content":{"rendered":"

In our previous tutorial, we studied Scala trait Mixins<\/a>\u00a0<\/strong>and now we are going to discuss\u00a0Scala constructor and types of constructor in Scala Programming Language<\/strong><\/a>: Primary Constructor and\u00a0Auxiliary Constructors in Scala. At last, we will cover Constructor Overloading in Scala.<\/p>\n

So, let’s begin Scala Constructor Tutorial.<\/p>\n

\"Scala<\/a>

Scala Constructor – 2 Popular Types of Constructors in Scala<\/p><\/div>\n

Scala Constructor<\/h3>\n

Scala constructor is used for creating an instance of a class. There are two types of constructor\u00a0in Scala – Primary and Auxiliary. Not a special method, a constructor is different in Scala than in Java constructors<\/strong><\/a>. The class\u2019 body is the primary constructor and the parameter list follows the class name. The following, then, is the default primary constructor.
\nLet’s see Scala Currying Function \u2013 Example & Partially Applied Function<\/a><\/strong><\/p>\n

Default Primary Constructor in Scala<\/h3>\n
scala>class Vehicle{\r\n| println(\"I am in the default constructor\")\r\n| }\r\ndefined class Vehicle\r\nscala> val v=new Vehicle()<\/pre>\n
I am in the default constructor
\nv: Vehicle = Vehicle@78288f83<\/strong>
\nHere, the class body has one print statement. This is the code in the default constructor. We could also have defined it without parentheses:<\/p>\n
scala> val v=new Vehicle<\/pre>\n
I am in the default constructor
\nv: Vehicle = Vehicle@7c751692<\/strong><\/p>\n
A Primary Constructor in Scala<\/h3>\n
A class in Scala may have only one primary constructor. Such a constructor may have zero or more parameters.<\/p>\n
scala> class Vehicle(model:String){\r\n| println(\"I am a \"+model+\".\")\r\n| }\r\ndefined class Vehicle\r\nscala> val v=new Vehicle(\"Brio\")<\/pre>\n
I am a Brio.
\nv: Vehicle = Vehicle@42cfd794<\/strong>
\nRead about Scala Method Overloading with Example<\/a><\/strong>
\nHere, a model is a val; we cannot reassign it. Take a look:<\/p>\n
scala> class Vehicle(model:String){\r\n| println(\"I am a \"+model+\".\")\r\n| model=\"Verna\"\r\n| println(\"I am now a \"+model+\".\")\r\n| }\r\n<console>:13: error: reassignment to val\r\nmodel=\"Verna\"\r\n^<\/pre>\n
But we can declare it to be a var:<\/p>\n
scala> class Vehicle(var model:String){\r\n| println(\"I am a \"+model+\".\")\r\n| model=\"Verna\"\r\n| println(\"I am now a \"+model+\".\")\r\n| }\r\ndefined class Vehicle\r\nscala> val v=new Vehicle(\"Brio\")<\/pre>\n
I am a Brio.
\nI am now a Verna.
\nv: Vehicle = Vehicle@11174bf<\/strong>
\nIn this case, the compiler generates setter and getter methods for the var.
\nTake another example:<\/p>\n
object Main extends App{\r\nclass Vehicle(model:String,color:String){\r\nprintln(\"I am a \"+color+\" \"+model+\".\")\r\n}\r\nvar v=new Vehicle(\"Verna\",\"red\")\r\n}<\/pre>\n
In the command prompt, using the Java Class File Disassembler:
\nC:\\Users\\lifei\\Desktop>javap Main.class<\/strong>
\nCompiled from “prim.scala”<\/strong><\/p>\n
public final class Main {\r\npublic static void main(java.lang.String[]);\r\npublic static void delayedInit(scala.Function0<scala.runtime.BoxedUnit>);\r\npublic static void delayedEndpoint$Main$1();\r\npublic static long executionStart();\r\npublic static void v_$eq(Main$Vehicle);\r\npublic static Main$Vehicle v();\r\n}<\/pre>\n
Let’s discuss Scala Object \u2013 Scala Singleton & Scala Companion Object<\/a><\/strong><\/p>\n
Auxiliary Constructors in Scala<\/h3>\n
A class may have any number of auxiliary constructors. You must make sure that it must make a call to another auxiliary constructor or to the primary constructor in the first line of its body. Hence, each auxiliary constructor directly or indirectly invokes the primary constructor.
\nLet\u2019s take an example.<\/p>\n
scala> class Vehicle(model:String,color:String){\r\n| var year:Int=2000\r\n| def show(){\r\n| println(\"I am a \"+color+\" \"+model+\" from \"+year)\r\n| }\r\n| def this(model:String,color:String,year:Int){\r\n| this(model,color) \/\/Call to the primary constructor\r\n| this.year=year\r\n| }\r\n| }\r\ndefined class Vehicle\r\nscala> var v=new Vehicle(\"Verna\",\"red\",2015)<\/pre>\n
v: Vehicle = Vehicle@18dd7767<\/strong><\/p>\n
scala> v.show()<\/pre>\n
I am a red Verna from 2015<\/p>\n
scala> var v1=new Vehicle(\"Verna\",\"black\")<\/pre>\n
v1: Vehicle = Vehicle@b2d8dcd<\/p>\n
scala> v1.show()<\/pre>\n
I am a black Verna from 2000
\nDo you know about Scala File i\/o: Open, Read and Write a File in Scala<\/a><\/strong><\/p>\n
Scala Constructor Overloading<\/h3>\n
Finally, let us take a look at how to overload constructors.<\/p>\n
scala> class Vehicle(model:String){\r\n| def this(model:String,color:String)={\r\n| this(model)\r\n| println(\"I am a \"+color+\" \"+model)\r\n| }\r\n| println(model)\r\n| }\r\ndefined class Vehicle\r\nscala> new Vehicle(\"Prius\")<\/pre>\n
Prius<\/p>\n
res2: Vehicle = Vehicle@421d7900\r\nscala> new Vehicle(\"Prius\",\"silver\")<\/pre>\n
Prius
\nI am a silver Prius
\nres3: Vehicle = Vehicle@42ea14b8
\nThis lets us make a call to the constructor that suits the number of arguments we provide.
\nHave a Look at Scala String Method with Syntax and Method<\/a><\/strong>
\nSo, this was all about Scala Constructor. Hope you like our explanation of types of Constructor in Scala.<\/p>\n
Conclusion<\/h3>\n
Hence, in this Scala constructor tutorial, we studied types of constructor:\u00a0Primary Constructor and\u00a0Auxiliary Constructors in Scala. In Addition, we will cover constructor overloading in Scala Programming Language.
\nRelated Article-\u00a0Scala Data Types with Examples\u00a0<\/a><\/strong>
\nFor reference\u00a0<\/a><\/strong>
In our previous tutorial, we studied Scala trait Mixins\u00a0and now we are going to discuss\u00a0Scala constructor and types of constructor in Scala Programming Language: Primary Constructor and\u00a0Auxiliary Constructors in Scala. At last, we will...<\/p>\n","protected":false},"author":6,"featured_media":18118,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[61],"tags":[1275,2930,2938,9959,12421,12422,12423,15108],"class_list":["post-18090","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-scala","tag-auxiliary-constructors-in-scala","tag-constructor-in-scala","tag-constructors-in-scala","tag-primary-constructor-in-scala","tag-scala-constructor","tag-scala-constructor-overloading","tag-scala-constructors","tag-types-of-scala-constructor"],"yoast_head":"\nScala Constructor - 2 Popular Types of Constructors in Scala - DataFlair<\/title>\n<meta name=\"description\" content=\"What is Scala Constructor - Types of Constructor in Scala, Default Primary Constructor in Scala, Primary Constructors & Auxiliary Constructors in Scala\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/data-flair.training\/blogs\/scala-constructor\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Scala Constructor - 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