Is it possible to call Swift convenience initializer in Objective-C

Yes we can use it Note: @objc and public are important

 @objc public init(url: URL) { 
   //your code 
 }

Check out Using Swift with Cocoa and Objective-C (Swift 2.2) - Mix and Match. What it seems to come down to is

1. Making your convenience initializer public, and
2. Importing an XCode-generated header file [YourProductModuleName]-Swift.h into your code

Please note! If you are using any of Swift features that are not available in Objective-C (like Optional values), it would not be accessible in Objective-C. So fix them.

 public convenience init(title:String?, message:String?) {
    self.init()
    self.title = title
    self.message = message
}

Above code is not accessible, so removing optional will help in this case.