Kotlin Named Arguments
Making function calls clearer and more flexible
🏷️ What are Named Arguments?
Named arguments let you specify parameter names when calling functions. This makes code more readable, allows parameter reordering, and helps avoid mistakes with multiple parameters.
fun createUser(name: String, age: Int, email: String) {
println("User: $name, Age: $age, Email: $email")
}
fun main() {
// Using named arguments
createUser(name = "Alice", age = 25, email = "[email protected]")
createUser(email = "[email protected]", name = "Bob", age = 30)
}
Output:
User: Alice, Age: 25, Email: [email protected]
User: Bob, Age: 30, Email: [email protected]
Named Arguments Benefits
Readability
Makes function calls self-documenting
// Clear what each value represents
connect(host = "localhost", port = 8080)Flexibility
Change parameter order freely
// Order doesn't matter
draw(color = "red", x = 10, y = 20)Safety
Prevents parameter mix-ups
// No confusion between width/height
resize(width = 800, height = 600)Selective
Skip middle parameters easily
// Skip middle parameter
format(text = "Hello", uppercase = true)🔹 Basic Named Arguments
Use parameter names followed by = when calling functions:
fun formatText(
text: String,
fontSize: Int,
color: String,
bold: Boolean
) {
val style = if (bold) "bold" else "normal"
println("Text: '$text' | Size: ${fontSize}px | Color: $color | Style: $style")
}
fun main() {
// Traditional positional arguments
formatText("Hello", 16, "blue", true)
// Named arguments (more readable)
formatText(
text = "World",
fontSize = 20,
color = "red",
bold = false
)
// Mixed approach
formatText("Kotlin", fontSize = 18, color = "green", bold = true)
}Output:
Text: 'Hello' | Size: 16px | Color: blue | Style: bold
Text: 'World' | Size: 20px | Color: red | Style: normal
Text: 'Kotlin' | Size: 18px | Color: green | Style: bold
🔹 Named Arguments with Default Values
Named arguments work perfectly with default parameters:
fun configureServer(
host: String = "localhost",
port: Int = 8080,
ssl: Boolean = false,
timeout: Int = 30,
maxConnections: Int = 100
) {
println("Server Config:")
println(" Host: $host:$port")
println(" SSL: $ssl")
println(" Timeout: ${timeout}s")
println(" Max Connections: $maxConnections")
println("---")
}
fun main() {
// Use only defaults
configureServer()
// Override specific parameters
configureServer(port = 9000, ssl = true)
// Skip middle parameters
configureServer(host = "production.com", timeout = 60)
}Output:
Server Config:
Host: localhost:8080
SSL: false
Timeout: 30s
Max Connections: 100
---
Server Config:
Host: localhost:9000
SSL: true
Timeout: 30s
Max Connections: 100
---
Server Config:
Host: production.com:8080
SSL: false
Timeout: 60s
Max Connections: 100
---
🔹 Mixing Positional and Named Arguments
You can combine positional and named arguments (positional must come first):
fun createButton(
text: String,
width: Int,
height: Int,
backgroundColor: String = "gray",
textColor: String = "black",
enabled: Boolean = true
) {
val status = if (enabled) "enabled" else "disabled"
println("Button: '$text' (${width}x${height}) | BG: $backgroundColor | Text: $textColor | $status")
}
fun main() {
// All positional
createButton("Click Me", 100, 50)
// Positional + named
createButton("Submit", 120, 40, backgroundColor = "blue", textColor = "white")
// Mixed with skipping
createButton("Cancel", 80, 35, textColor = "red", enabled = false)
}Output:
Button: 'Click Me' (100x50) | BG: gray | Text: black | enabled
Button: 'Submit' (120x40) | BG: blue | Text: white | enabled
Button: 'Cancel' (80x35) | BG: gray | Text: red | disabled