Argument type 'LanguageItem?' does not conform to expected type 'CVarArg'

Question

imneo OP

Created Aug ’23

Replies 2

Boosts 0

Participants 3

I have the following code:

let obj: LanguageItem? = LanguageItem(language: "zh-CN")
// Argument type 'LanguageItem?' does not conform to expected type 'CVarArg'
print(String(format:"obj: %@", obj))

struct LanguageItem: Codable
{
    var language: String
    var name: String?
}

How can I make my class work with String(format:)?

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Answer 1

Claude31 OP

Aug ’23

That's logical.

%@ expects a String parameter. LanguageItem is not a String.

What do you want to print ?

You have several options:

pass the language property

print(String(format:"obj: %@", (obj?.language ?? "")))

if you want to print the compete struct, create a description var:

struct LanguageItem: Codable {
    var language: String
    var name: String?
    
    var description: String {
        return language + (name ?? "")
    }
}
let obj: LanguageItem? = LanguageItem(language: "zh-CN")

print(String(format:"obj: %@", (obj?.description ?? "")))

0

Answer 2

DTS Engineer OP

Apple

Aug ’23

How can I make my class work with String(format:)?

The technically correct approach is to conform your type to CustomStringConvertible:

https://developer.apple.com/documentation/swift/customstringconvertible/

0