Is there a way to make a Kotlin class implement the Swift

Error

protocol in the ios part of my MPP project? NOT

NSError

No.

That’s what I thought, thanks for the confirmation. I have a hard time with the “no inheritance under an ObjC/Swift class” but I’ll find a way

I have a hard time with the “no inheritance under an ObjC/Swift class”

What do you mean?

We’re making a logging mpp library which passes errors to Bugsnag through their Android & iOS clients. I would like to have a

BugsnagError

class which would be the super class of all our errors and in which we could add metadata to appear on the Bugsnag interface. It’s not possible easily because the iOS

BugsnagError

class cannot both be

open

and extend

NSError

. I can have it embed a

NSError

, but then it cannot be thrown from Swift because it does not implement the

Error

protocol.

You can wrap it to

NSError

instead.

What do you mean ?

NSError

can contain arbitrary data in

userInfo

dictionary. So you can throw

NSError

containing

BugsnagError

instance.

I suppose that’s possible but

userInfo

is final and can’t be modified after the

NSError

is created. That prevents me from having a nice feature: adding metadata to an error after it has been created. Typically, I would add call-site information to an error returned by a webservice implementation before sending it to the logger. I don’t think we can work without that feature... I could wrap an error in another one every time I add data to it but then the code retrieving this data before sending it to bugsnag needs to become recursive and take duplicates into account... It makes a lot of things much harder

If

BugsnagError

was an

Error

, you would throw it. It is not, so you can * Throw

NSError(userInfo: { "BugsnagError" : bugsnagError })

instead of

bugsnagError

* Check that

NSError

has

"BugsnagError"

key instead of checking that error is

BugsnagError

* Modify

NSError.userInfo["BugsnagError"]

object instead of modifying a caught error directly. How can this make some code recursive? You can handle special

NSError

the same way you’d handle

BugsnagError

.

You can modify

NSError.userInfo["BugsnagError"]

? I thought

userInfo

was a

val

You can modify contents of

NSError.userInfo["BugsnagError"]

, i.e. the object from

userInfo

.

Oh, you mean that I could modify the

BugsnagError

instance, like calling methods on it etc, but not replace it

Yes. Alternatively you can throw new NSError instance with new BugsnagError inside. What I'm trying to say is that wrapping to NSError doesn't affect the operations available.