抛出方法不能是@objc协议的成员，因为它返回类型'Bool'的值

Question

I get following error:

Throwing method cannot be a member of an @objc protocol because it returns a value of type 'Bool'; return 'Void' or a type that bridges to an Objective-C class

When defining Swift protocol which also needs to be bridged to Objective-C:

@objc public protocol Saving {

    func save() throws -> Bool
}

Is there an other way to define Swift method which can return Bool , potentially throw an error and be Objetive-C compatible?

Answer 1

As indicated in the comments, the following in Swift:

func save() throws

will be translated into:

(BOOL)saveAndReturnError:(NSError **)error

in Objective-C. Which explains the limitation.

I know that in the save() example, it might not make much sense to return a Bool as well as throwing, but I disagree with the comment about it not making sense at all. There might be other use cases where it makes sense. Fx. the inverse example; loading Bool 's by using an identifer. Loading a Bool might return true / false or throw if loading fails, fx. if the identifier was not found when trying to load.

However unfortunately we cannot do this because of how Swift and Objective-C is being bridged.