Scala | Named Arguments
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 ); } } |
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 ) } } |
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.
