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Scala | Named Arguments
  • Last Updated : 08 Apr, 2019

In Scala when arguments passes through the function with a named parameters, we can label the arguments with their parameter names.These named arguments are cross matched with the named parameters of function. In normal scenario Unnamed Parameters uses Parameter Positions to make Function or Constructor calls, but These named parameters allows us to change order of the arguments passes to a function by simply exchanging the order.
Syntax:

Function Definition : def createArray(length:int, capacity:int);
Function calling : createArray(capacity=20, length:10);

Precautions –

-> If some arguments are named and others are not, the unnamed arguments must come first
function(0, b = "1")

-> Order Interchange is valid
function(b = "1", a = 0)

-> Not accepted , error: positional after named argument
function(b = "1", 0)



-> Not accepted , parameter ‘a’ specified twice as ‘0’ in first position and again as a = 1
function(0, a = 1)

Note : If x argument expression has the form x = expr and x is not a parameter name of the method, the argument is treated as an assignment expression to some variable x.

Example :




// Scala program using Named arguments
  
// Creating object
object GFG
{
    // Main method
    def main(args: Array[String])
    {
        // passed with named arguments 
        printIntiger(X = 6, Y = 8);
    }
      
    // Defining a method
    def printIntiger( X:Int, Y:Int ) = 
    {
        println("Value of X : " + X );
        println("Value of Y : " + Y );
    }
}
Output:
Value of X : 6
Value of Y : 8

Here, in above example we created the printIntiger function and then we called the function. we use the function parameter names when calling the function. we passed arguments X = 6 , Y = 8 here X and Y are the name of parameters.

Example :




// Scala program using Named arguments
  
// Creating object
object GFG
{
  
    // Main method
    def main(args: Array[String]) 
    {     
        // without named arguments 
        printName("geeks","for","geeks");
          
        // passed arguments according to order
        printName(first = "Geeks", middle="for"
                                last = "Geeks");
          
        // passed arguments with different order
        printName(last = "Geeks", first = "Geeks"
                                    middle="for");
    }
      
    // Defining function
    def printName( first: String, middle: String, 
                                    last: String ) = 
    {
        println("Ist part of name: " + first )
        println("IInd part of name: " + middle )
        println("IIIrd part of name: " + last )
    }
}
Output:
Ist part of name: geeks
IInd part of name: for
IIIrd part of name: geeks
Ist part of name: Geeks
IInd part of name: for
IIIrd part of name: Geeks
Ist part of name: Geeks
IInd part of name: for
IIIrd part of name: Geeks

As we can see in above example, we created the printName function, and then we called the function. Here, we use the function parameter names when calling the function. By changing the order of the arguments like printName(last = “Geeks”, first = “Geeks”, middle=”for”) we can get the same result.

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