Parameterless Method in Scala

Prerequisites – Scala | Functions

A parameterless method is a function that does not take parameters, defined by the absence of any empty parenthesis. Invocation of a paramaterless function should be done without parenthesis. This enables the change of def to val without any change in the client code which is a part of uniform access principle.

Example:



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// Scala program to illustrate
// Parameterless method invocation
class GeeksforGeeks(name: String, ar: Int)
{
    // A parameterless method
    def author = println(name)
    def article = println(ar)
      
    // An empty-parenthesis method
    def printInformation() = 
    {
        println("User -> " + name + ", Articles -> " + ar)
    }
}
  
// Creating object 
object Main 
    // Main method
    def main(args: Array[String]) 
    
          
        // Creating object of Class 'Geeksforgeeks'
        val GFG = new GeeksforGeeks("John", 50)
        GFG.author     // calling method without parenthesis
    

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Output:

John

There are generally two conventions for using parameter less method. One is when there are not any parameters. Second one is when method does not change the mutable state. One must avoid the invocations of parameterless methods which look like field selections by defining methods that have side-effects with parenthesis.
An example of calling a parameterless method with a parenthesis giving a Compilation error.

Example:

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// Scala program to illustrate
// Parameterless method invocation
class GeeksforGeeks(name: String, ar: Int)
{
    // A parameterless method
    def author = println(name)
    def article = println(ar)
      
    // An empty-parenthesis method
    def printInformation() = 
    {
        println("User -> " + name + ", Articles -> " + ar)
    }
}
  
// Creating object
object Main 
    // Main method
    def main(args: Array[String]) 
    
          
        // Creating object of Class 'Geeksforgeeks'
        val GFG = new GeeksforGeeks("John", 50)
        GFG.author()     //calling method without parenthesis
    

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Output:

prog.scala:23: error: Unit does not take parameters
GFG.author() //calling method without parenthesis
^
one error found

Note: An empty parenthesis method can be called without parenthesis but it is always recommended and accepted as convention to call empty-paren methods with parenthesis.



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