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this keyword in Scala

By IncludeHelp Last updated : October 22, 2024

'this' keyword

this keyword in Scala is used to refer to the object of the current class. Using this keyword you can access the members of the class like variables, methods, constructors.

In Scala, this keyword can be used in two different ways,

this with Dot (.) Operator

The dot (.) operator in Scala is used to call members of the current class. Both data members and member functions can be called using a dot (.) operator.

Syntax

this.member_name;

this will call members associated with the current object of the class. you can call any member associated using dot (.) operator.

Example

class Student {
  var name: String = ""
  var marks: Int = 0

  def info(name: String, marks: Int): Unit = {
    this.name = name
    this.marks = marks
  }

  def show(): Unit = {
    println("Student " + name + " has obtained " + marks + " marks.")
  }
}

object MyObject {
  def main(args: Array[String]): Unit = {
    val s1 = new Student()
    s1.info("Kabir", 473)
    s1.show()
  }
}

Output

Student Kabir has obtained 473 marks 

The above code is used to display implementation of this keyword with the dot operator. In the program, we have named students which contains some variables. In methods of the student class, we have used with this keyword with the dot operator to call data member of the class.

Using this()

In Scala programming language, constructors can be called using this keyword. this keyword is used to create the auxiliary constructors and Scala. For an auxiliary constructor, the first line in the constructor should be a call to another constructor to run without error.

Syntax

this(){
}

Here, this keyword is used to define a constructor that of the class. The constructor created is an auxiliary constructor that needs to call another auxiliary constructor or primary constructor in its call.

Example

class Students { 
  var name: String = ""
  var marks: Int = 0
	
  def this(name: String, marks: Int) { 
    this()
    this.name = name 
    this.marks = marks 
  } 
	
  def show(): Unit = {
    println("Student " + name + " has obtained " + marks + " marks") 
  } 
} 

object MyObject { 
  def main(args: Array[String]): Unit = { 
    val s1 = new Students("Kabir", 473) 
    s1.show()
  } 
}

Output

Student Kabir has obtained 473 marks 

Constructor calling by using this keyword

The "this" keyword is used to call another constructor from within a constructor in Scala. This feature allows constructor overloading.

Example

class Student(name: String) {  
  def this(name: String, age: Int) {  
    this(name)  
    println(s"Student's name is $name and age is $age")  
  }      
}  
  
object MainObject {  
  def main(args: Array[String]): Unit = {  
    val s = new Student("Aarav", 22)  
  }  
}

Output

Student's name is Aarav and age is 22