Scala: How to define a constructor?

Using ‘this()’ you can define a constructor.

Define default constructor

class Employee(id: Int, firstName: String, lastName: String) {

  def this() = {
    this(0, "no_name", "no_name")
  }

}

Define constructor with arguments

class Employee(id: Int, firstName: String, lastName: String) {
  def this(id: Int) = {
    this(id, "no_name", "no_name")
  }

  def this(id: Int, firstName: String) = {
    this(id, firstName, "no_name")
  }
}

Final Employee class looks like below.

class Employee(id: Int, firstName: String, lastName: String) {

  def this() = {
    this(0, "no_name", "no_name")
  }

  def this(id: Int) = {
    this(id, "no_name", "no_name")
  }

  def this(id: Int, firstName: String) = {
    this(id, firstName, "no_name")
  }

  def getId = {
    id
  }

  def getFirstName = {
    firstName
  }

  def getLastName = {
    lastName
  }

  override def toString = {
    s"id = $id, firstName: $firstName, lastName: $lastName"
  }

}

 Examples to define object using constructors.

val emp1 = new Employee()

val emp2 = new Employee(123)

val emp3 = new Employee(123, "Krishna")

val emp4 = new Employee(123, "Krishna", "Gurram")

Find the below working application.

scala> class Employee(id: Int, firstName: String, lastName: String) {
     | 
     |   def this() = {
     |     this(0, "no_name", "no_name")
     |   }
     | 
     |   def this(id: Int) = {
     |     this(id, "no_name", "no_name")
     |   }
     | 
     |   def this(id: Int, firstName: String) = {
     |     this(id, firstName, "no_name")
     |   }
     | 
     |   def getId = {
     |     id
     |   }
     | 
     |   def getFirstName = {
     |     firstName
     |   }
     | 
     |   def getLastName = {
     |     lastName
     |   }
     | 
     |   override def toString = {
     |     s"id = $id, firstName: $firstName, lastName: $lastName"
     |   }
     | 
     | }
class Employee

scala> val emp1 = new Employee()
val emp1: Employee = id = 0, firstName: no_name, lastName: no_name

scala> val emp2 = new Employee(123)
val emp2: Employee = id = 123, firstName: no_name, lastName: no_name

scala> val emp3 = new Employee(123, "Krishna")
val emp3: Employee = id = 123, firstName: Krishna, lastName: no_name

scala> val emp4 = new Employee(123, "Krishna", "Gurram")
val emp4: Employee = id = 123, firstName: Krishna, lastName: Gurram

 

 

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