Hello this is a pretty simple example code in the Playground , but at the line of name = name.uppercased(), Xcode warns me that error: cannot assign to value: 'name' is a 'let' constant

How come name is a constant ? I didn't declare it as a constant or a variable.

import Cocoa

func isUppercase(_ name: String) -> String {
   name = name.uppercased()
}

let result = isUppercase("Mary")

print (result)

@roosterboy thank you as alway !

noted about the convention too.

Happy Lunar New Year and have a great year of tiger !

Boat

As @roosterboy say parameters passing in are none mutating however if you want them to be you need to add inout eg

func toUppercase(_ name: inout String) -> String {
   name.uppercased()
}

And when you call it you need a & in front of the variable that you want to mutate.

var mary = "Mary"
let result = toUppercase(&mary)
print(result) // MARY

More detail explanation What are inout parameters?

@NigelGee thanks for the extensive explanation !

Will look into it !

have a great day,

Boat