When @objc and @nonobjc write before method and variable in swift?

Question

When I declare static parameter in extension of class then I have to write @nonobjc before variable like

 @nonobjc static let test = \"test\"

a

Answer 1

This is explained in the Apple's official documentation about Objective-C - Swift interoperability:

When you use the @objc(name) attribute on a Swift class, the class is made available in Objective-C without any namespacing. As a result, this attribute can also be useful when migrating an archivable Objective-C class to Swift. Because archived objects store the name of their class in the archive, you should use the @objc(name) attribute to specify the same name as your Objective-C class so that older archives can be unarchived by your new Swift class.

Conversely, Swift also provides the @nonobjc attribute, which makes a Swift declaration unavailable in Objective-C. You can use it to resolve circularity for bridging methods and to allow overloading of methods for classes imported by Objective-C. If an Objective-C method is overridden by a Swift method that cannot be represented in Objective-C, such as by specifying a parameter to be a variable, that method must be marked @nonobjc.

To summarize, use @objc when you want to expose a Swift attribute to Objective-C without a namespace . Use @nonobjc if you want to keep the attribute available and accessible only in Swift code.