🔸argument label

Swift ⟩ basic types ⟩ function ⟩ argument label

// • AL: (argument label) for outer call sites. ⭐️
// • PN: (parameter name) for inner implementation.
//
//         ╭─AL─╮ ╭PN╮          ╭AL╮ ╭──PN──╮
func greet(person name: String, from hometown: String)

when you assign a function to a variable, you can't use argument labels on calling the function through that variable. 👉 see： function as variable

replit：argument label vs. parameter name

@discardableResult    // to silence compiler warnings

// ⭐️ argument label vs. paramter name
// --------------------------------------------------
//   • AL: (argument label) for outer call sites.
//   • PN: (parameter name) for inner implementation.

// ⭐️ function declaration
//
//         ╭─AL─╮ ╭PN╮          ╭AL╮ ╭──PN──╮
func greet(person name: String, from hometown: String) -> String {
    
    // ⭐️ PN (parameter names) used inside (implementation)
    //
    //                 ╭PN╮                                ╭──PN──╮
    let msg = "Hello \(name)!  Glad you could visit from \(hometown)."
    
    print(msg)
    return msg
}

// ⭐️ call site
//
//    ╭─AL─╮          ╭AL╮  <----  ⭐️ AL: (argument labels) used outside
greet(person: "Bill", from: "Cupertino")
//            ╰arg─╯        ╰── arg ──╯
//
// • the real values put into functions are call "arguments".
// • this is why the labels before them are call "argument labels".

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Last updated 2 years ago