Scala Field Overriding

by Online Tutorials Library July 14, 2022

Scala Field Overriding

In scala, you can override fields also but it has some rules that need to be followed. Below are some examples that illustrate how to override fields.

Scala Field Overriding Example1

 class Vehicle{     var speed:Int = 60  } class Bike extends Vehicle{    var speed:Int = 100     def show(){         println(speed)     } } object MainObject{     def main(args:Array[String]){         var b = new Bike()         b.show()     } } 

Output:

Error - variable speed needs 'override' modifier

In scala, you must use either override keyword or override annotation when you are overriding methods or fields of super class. If you don’t do this, compiler reports an error and stops execution of program.

Scala Field Overriding Example2

 class Vehicle{      val speed:Int = 60  } class Bike extends Vehicle{    override val speed:Int = 100// Override keyword     def show(){         println(speed)     } } object MainObject{     def main(args:Array[String]){         var b = new Bike()         b.show()     } } 

Output:

In scala, you can override only those variables which are declared by using val keyword in both classes. Below are some interesting examples which demonstrate the whole process.

Scala Field Overriding Example3

 class Vehicle{      var speed:Int = 60 } class Bike extends Vehicle{    override var speed:Int = 100     def show(){         println(speed)     } } object MainObject{     def main(args:Array[String]){         var b = new Bike()         b.show()     } } 

Output:

variable speed cannot override a mutable variable

Scala Field Overriding Example4

 class Vehicle{      val speed:Int = 60  }  class Bike extends Vehicle{    override var speed:Int = 100     def show(){         println(speed)     } }  object MainObject{     def main(args:Array[String]){         var b = new Bike()         b.show()     } } 

Output:

Error - variable speed needs to be a stable, immutable value

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Scala Field Overriding

Scala Field Overriding

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Scala Field Overriding Example2

Scala Field Overriding Example3

Scala Field Overriding Example4

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