Encapsulation in Scala: Protecting and Managing Data | CodeSignal Learn

Encapsulation in Scala: Protecting and Managing Data | CodeSignal Learn

Let's illustrate encapsulation with an example and delve deeper into accessors and mutators:

class Person(private var _name: String, private var _age: Int):
  def name: String = _name // Accessor method for 'name'
  def name_=(newName: String): Unit = _name = newName // Mutator method for 'name'

  def age: Int = _age // Accessor method for 'age'
  def age_=(newAge: Int): Unit = _age = newAge // Mutator method for 'age'
  
@main def main(): Unit =
  val person = Person("Alice", 30) // Create a Person object
  person.name = "Bob" // Set name via mutator
  person.age = 25 // Set age via mutator
  println(s"Name: ${person.name}, Age: ${person.age}")

In this example, the Person class encapsulates the properties _name and _age by declaring them as private. To manipulate this properties, we introduce two types of (public) methods:

Accessors: Also known as "getter" methods, accessors are used to retrieve the current value of a private field. For example, the name method is an accessor that returns the value of _name.
Mutators: Also known as "setter" methods, mutators are used to modify the value of a private field. In Scala, you create a mutator by defining a method with the property name followed by _=. This is a Scala-specific convention that allows you to mimic assignment syntax: for example, the name_= method allows external code to modify the _name field, while maintaining control over the assignment.

By using accessors and mutators, we maintain control over how external code interacts with the object's state, ensuring that changes to private fields are performed in a controlled and predictable manner.

Validating Data with Accessors and Mutators

Encapsulation allows you to include validation logic within your accessors and mutators. This ensures that any changes to the object's state meet certain criteria, maintaining data integrity. // Mutator for 'age' with validation def age_=(newAge: Int): Unit = if newAge >= 0 then _age = newAge else println("Invalid age") By adding a simple check, we prevent the age from being set to a negative number. This validation helps maintain a consistent and valid state within the Person object.

Scala

class Person(private var _name: String, private var _age: Int):
  def name: String = _name // Accessor method for 'name'
  def name_=(newName: String): Unit = _name = newName // Mutator method for 'name'

  def age: Int = _age // Accessor method for 'age'
  def age_=(newAge: Int): Unit = _age = newAge // Mutator method for 'age'
  
@main def main(): Unit =
  val person = Person("Alice", 30) // Create a Person object
  person.name = "Bob" // Set name via mutator
  person.age = 25 // Set age via mutator
  println(s"Name: ${person.name}, Age: ${person.age}")