Named Arguments and Default Parameter Values in Scala | CodeSignal Learn

Named Arguments and Default Parameter Values in Scala | CodeSignal Learn

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Topic Overview

Welcome! This Scala lesson demystifies two key features: named arguments and default parameter values . They make function calls clearer and the code more maintainable.

Named Arguments in Scala

Default Parameter Values in Scala

Default parameter values automatically assign a predefined value to a function parameter. They permit the skipping of parameters that aren't required for the function call. Consider a function that greets a user: Scala def greetUser(name: String = "Guest"): Unit = println(s"Hello, $name") @main def run: Unit = greetUser() // Displays "Hello, Guest" greetUser("John") // Displays "Hello, John" greetUser(name = "Emily") // Displays "Hello, Emily" The first function call uses the default value, as no argument is passed.

Combining Named Arguments and Default Parameter Values

Lesson Summary and Upcoming Practice

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Named arguments enhance code readability by associating each argument with a parameter name, thereby eliminating the need to remember their order. When using named arguments, you can place them in any order during the function invocation.

Imagine you're drawing a rectangle:

Scala

def drawRectangle(height: Int, width: Int, color: String): Unit =
    println(s"Drawing a rectangle of height $height, width $width, and color $color")

@main def run: Unit =
    drawRectangle(height = 5, color = "blue", width = 10)
    drawRectangle(height = 5, width = 10, color = "blue")
    drawRectangle(color = "blue", width = 10, height = 5)

Named arguments make function invocations self-explanatory, reducing errors and improving readability.

The combination of both concepts brings flexibility and clarity.

Let's modify the drawRectangle function, adding a default color:

Scala

def drawRectangle(height: Int, width: Int, color: String = "Red"): Unit =
    println(s"Drawing a rectangle of height $height, width $width, and color $color")

@main def run: Unit =
    drawRectangle(height = 20, width = 30)                      // color is "Red"
    drawRectangle(height = 20, color = "Blue", width = 30)      // color is "Blue"