Swift print() error

Question

Created Aug ’20

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I'm developing a macOS document-based app in Swift, using Xcode 11.6 and the template it provides. I often use Swift print() statements during development to see what's going on as the app runs. But when I try to put one of these in the Document.swift template file, I get errors:

Cannot convert value of type 'String' to expected argument type '[NSPrintInfo.AttributeKey : Any]'

Missing argument label 'withSettings:' in call

Missing arguments for parameters 'showPrintPanel', 'delegate', 'didPrint', 'contextInfo' in call

I don't get these errors when I put a print() statement in the AppDelegate.swift or ViewController.swift files. Can someone tell me what the problem is here?

Answered by OOPer in 627626022

Under the current Xcode (11.6), Xcode imports the class NSDocument as having a method print(withSettings:showPrintPanel:delegate:didPrint:contextInfo:), so, it may be shadowing the Swift.print you want to use.

Underlying Objective-C method is printDocumentWithSettings:showPrintPanel:delegate:didPrintSelector:contextInfo:, so it should be imported as printDocument(withSettings:showPrintPanel:delegate:didPrint:contextInfo:).
(As far as I remember, the Objective-C name was renamed to avoid confusion in Swift code a little time ago.)

In my opinion, this is a bug of the macOS SDK bundled with Xcode 11.6, and you should better send a feedback to Apple.

Until the issue is fixed, you can workaround using Swift.print instead of print.

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Answer 1

Claude31 OP

Aug ’20

Could you show the code where this occurs ? And tell what the context is (in which class does this occur).

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Answer 2

OOPer OP

Aug ’20

Accepted Answer

Under the current Xcode (11.6), Xcode imports the class NSDocument as having a method print(withSettings:showPrintPanel:delegate:didPrint:contextInfo:), so, it may be shadowing the Swift.print you want to use.

Underlying Objective-C method is printDocumentWithSettings:showPrintPanel:delegate:didPrintSelector:contextInfo:, so it should be imported as printDocument(withSettings:showPrintPanel:delegate:didPrint:contextInfo:).
(As far as I remember, the Objective-C name was renamed to avoid confusion in Swift code a little time ago.)

In my opinion, this is a bug of the macOS SDK bundled with Xcode 11.6, and you should better send a feedback to Apple.

Until the issue is fixed, you can workaround using Swift.print instead of print.

0

Answer 3

Albinus OP

Aug ’20

Thanks to OOPer for the explanation and the solution!

0