Update README for Swift to avoid "A C function pointer can only be formed from a reference to a 'func' or a literal closure" Error

I copied the code from the README file into my AppDelegate and got an error saying “A C function pointer can only be formed from a reference to a ‘func’ or a literal closure”. This was due to the fact your are passing the instance method registerPlugins as an argument into the FlutterDownloaderPlugin.setPluginRegistrantCallback method. This seems to be due to an issue bridging with Objective C.

Fortunately this stack overflow answer pointed me in the right direction and I was able to solve it by instead passing a closure as an argument like so:

FlutterDownloaderPlugin.setPluginRegistrantCallback { registry in
        if (!registry.hasPlugin("FlutterDownloaderPlugin")) {
           FlutterDownloaderPlugin.register(with: registry.registrar(forPlugin: "FlutterDownloaderPlugin")!)
        }
}

The README should be updated so that it works.

[gazialankus]

It needs the exclamation mark on my end. Without the exclamation mark I get

Argument type 'FlutterPluginRegistrar?' does not conform to expected type 'FlutterPluginRegistrar'

[Drabuna]

Helpful, thanks! Except you don’t need exclamation mark at the end here:

FlutterDownloaderPlugin.register(with: registry.registrar(forPlugin: "FlutterDownloaderPlugin")!)