Exception Handling in Swift

KalS

Hello, we've been having some issues with NSException handling in our app. The crashes are not consistent but usually occur in the client.subscribeTableWithExtendedInfo: method:

*** Terminating app due to uncaught exception 'Lightstreamer server exception', reason: 'Server exception (reason: 'Lightstreamer sync error received')'
*** First throw call stack:
(0x29117f8f 0x37a64c8b 0x9da1bb 0x9ce965 0x9cdf31 0x9cddd7 0x24a784 0xfe850 0x27af173 0x27b9c39 0x27bae19 0x38159db5 0x38159b08)
libc++abi.dylib: terminating with uncaught exception of type LSPushServerException

I've read your forum posts and you mostly say that we should handle the exceptions, which is fine, but you use NSException which is not catchable in Swift. Do you have any suggestions or insights as to how we can handle this optimally?

gianluca.bertani

Sorry, we encountered an error while displaying this content. If you're a user, please try again later. If you're an administrator, take a look in your Flarum log files for more information.

KalS

Thank you for the quick reply, we'll check the newest version.

jpsauvager

Hi all,

I have issues catching exception in Swift as well with the following code:

public func unsubscibeElement(tableKey tableKey: LSSubscribedTableKey) {

do {
//self.client is an instance of LSClient
try self.client.unsubscribeTable(tableKey, error: ())
}
catch {
print("Error occured")
}
}

It does not catch LSPushClientException "Table not found". This version of the unsubscribe function becomes throwing in Swift but it looks like there is a little interoperability issue.

Thanks for your help.

gianluca.bertani

Hello,

the LSPushClientExceptionis one of those exceptions related to programming errors that are not wrapped in an NSError. In particular, a "Table not found" is probably due to unsubscribing the same table twice. This is also stated in the method documentation .

Best regards,

Gianluca

Alessandro Alinone

@jpsauvager, as mentioned in a previous post, you might want to check out the new version of the iOS API for Lightstreamer (the Unified Client API). It throws no such exceptions but rather delivers them asynchronously via the subscription delegate. You can find full details here: http://blog.lightstreamer.com/2015/10/new-client-apis-for-ios-and-os-x.html