Classes, Constructors, Named Parameters

Here I compare these aspects :

How are objects created
Support of named parameters

Groovy

If the first parameter is a map, then named parameters are supported as elements of this map
This only works for the first parameter, it does not work for any other position, even if it is a map
If you omit these named parameters, the map will be null

If there are other parameters after the map, you have to pass at least one named parameter or it will not compile

class GT2 {

    int i
    String s

    GT2(aMap) {
        i = aMap.anInt
        s = aMap.aString
    }

    String f(aMap) {
        if (aMap == null) {
            return s + i + " : -\n"
        } else {
            return s + i + " : " + aMap.otherInt + aMap.otherString + "\n"
        }
    }
                
    String g(def aMap, i) {
        if (aMap == null) {
            return "output : " + i + "\n"
        } else {
            return "output : " + aMap.otherInt + aMap.otherString + "\n"
        }
    }
}
  
GT2 gt2 = new GT2(anInt:  1, aString : "A")
print gt2.f(otherInt: 2, otherString: "B")
print gt2.f()
print gt2.g(otherInt: 3, otherString: "C",101)
print gt2.g(otherInt: 4, otherString: "D", lalala : 17, 102)

You can put the named parameters where ever you want

If you want to pass an empty map or a not existing map, it must be the first parameter in the function call

String h(aMap, i, j, k) {
  if (aMap == null) {
      return "output : " + i + j + k + "\n"
  } else {
      return "output : " + aMap.otherInt + aMap.otherString + i + j + k + "\n"
  }
}

print gt2.h(101, "17", 307, otherInt: 5, otherString: "e")
print gt2.h(101, otherInt: 6, otherString: "f","17", 307 )
print gt2.h(101, otherInt: 7, "17", otherString: "g",  307)
print gt2.h(null , 101, "17", 307)

Kotlin

Kotlin supports primary and secondary constructors plus initializers
In this comparison I only use primary constructors
Constructors specify if values are constant or variable
function parameters seem always to be constants, but I have not investigated this any further yet
Both constructors and functions support real named parameters

Both constructors and functions support default values

class K2(val a : Int = 99, val b : String = "Z")

fun printValues(a : Int = 0, b : String = "a") {
    print("values : ")
    print(a)
    print(b)
    print("\n")
}

fun main(args: Array<String>) {

    val k21 = K2(1, "A")
    printValues(k21.a, k21.b)
    printValues( a = k21.a, b = k21.b)
    printValues( b = k21.b, a = k21.a)
    printValues( a = k21.a)
    printValues( b = k21.b)
    printValues()

    val k22 = K2( b = "B")
    printValues(k22.a, k22.b)
    printValues( a = k22.a, b = k22.b)
    printValues( b = k22.b, a = k22.a)
    printValues( a = k22.a)
    printValues( b = k22.b)
    printValues()

    val k23 = K2( b = "C", a = 3)
    printValues(k23.a, k23.b)
    printValues( a = k23.a, b = k23.b)
    printValues( b = k23.b, a = k23.a)
    printValues( a = k23.a)
    printValues( b = k23.b)
    printValues()

    val k24 = K2( a = 4)
    printValues(k24.a, k24.b)
    printValues( a = k24.a, b = k24.b)
    printValues( b = k24.b, a = k24.a)
    printValues( a = k24.a)
    printValues( b = k24.b)
    printValues()

    val k25 = K2(5)
    printValues(k25.a, k25.b)
    printValues( a = k25.a, b = k25.b)
    printValues( b = k25.b, a = k25.a)
    printValues( a = k25.a)
    printValues( b = k25.b)
    printValues()

    val k26 = K2( a = 6)
    printValues(k26.a, k26.b)
    printValues( a = k26.a, b = k26.b)
    printValues( b = k26.b, a = k26.a)
    printValues( a = k26.a)
    printValues( b = k26.b)
    printValues()
}

Swift

Swift supports multiple constructors with the name init, called initializers
Both constructors and functions support real named parameters
Both constructors and functions support default values
Both constructors and functions demand that the order of named arguments may not be changed
Swift supports unnamed arguments (underscore operator), I have not analyzed this here
When using named parameters, you must use them, even if there is no other initializer as alternative available

Swift supports different initializers with different parameters, same argument number and default values, I have not analyzed this here

class K2 {
    let a : Int
    let b : String

    init (x : Int = 99, y : String = "Z") {
        a = x
        b = y
    }

    init (q : Bool) {
        if (q) {
            a = 7
            b = "U"
        } else {
            a = 9
            b = "V"
        }
    }
}

func printValues(a : Int = 0, b : String = "a") {
    print("values : ")
    print(a)
    print(b)
    print("\n")
}

let k20a = K2(q:true)
printValues( a : k20a.a, b : k20a.b)
let k20b = K2(q:false)
printValues( a : k20b.a, b : k20b.b)

let k21 = K2( x : 1, y : "A")
// printValues( k21.a, k21.b) is forbidden due to missing argument names
printValues( a : k21.a, b : k21.b)
// printValues( b : k21.b, a : k21.a) is forbidden due to argument order
printValues( a : k21.a)
printValues( b : k21.b)
printValues()

let k22 = K2( y : "B")
printValues( a : k22.a, b : k22.b)
printValues( a : k22.a)
printValues( b : k22.b)
printValues()

// let k23 = K2( b : "C", a : 3) is forbidden due to argument order

let k24 = K2( x : 4)
printValues( a : k24.a, b : k24.b)
printValues( a : k24.a)
printValues( b : k24.b)
printValues()

// let k25 = K2(5) is forbidden due to missing argument name

let k26 = K2( x : 6)
printValues( a : k26.a, b : k26.b)
printValues( a : k26.a)
printValues( b : k26.b)
printValues()

Python

Python supports named parameters in but you don’t need to use the names
When using named parameters you may change the order of parameters

There is no difference between function and constructor regarding named parameters

class K2:

    def __init__(self, x = 1, y = "A"):
        self.a = x
        self.b = y

def printValues(a = 7,b = "Q"):
    print(a)
    print(b)

k21 = K2()
printValues(k21.a, k21.b)
printValues(a = k21.a, b = k21.b)
printValues(b = k21.b, a = k21.a)
printValues(b = k21.b, a = k21.a)
printValues(b = k21.b)
printValues(a = k21.a)
printValues()

k22 = K2(x = 5,y = "D")
printValues(k22.a, k22.b)
printValues(a = k22.a, b = k22.b)
printValues(b = k22.b, a = k22.a)
printValues(b = k22.b, a = k22.a)
printValues(b = k22.b)
printValues(a = k22.a)
printValues()

k23 = K2(y = "E", x = 6)
printValues(k23.a, k23.b)
printValues(a = k23.a, b = k23.b)
printValues(b = k23.b, a = k23.a)
printValues(b = k23.b, a = k23.a)
printValues(b = k23.b)
printValues(a = k23.a)
printValues()

k24 = K2(y = "F")
printValues(k24.a, k24.b)
printValues(a = k24.a, b = k24.b)
printValues(b = k24.b, a = k24.a)
printValues(b = k24.b, a = k24.a)
printValues(b = k24.b)
printValues(a = k24.a)
printValues()

k25 = K2(x = 8)
printValues(k25.a, k25.b)
printValues(a = k25.a, b = k25.b)
printValues(b = k25.b, a = k25.a)
printValues(b = k25.b, a = k25.a)
printValues(b = k25.b)
printValues(a = k25.a)
printValues()