Not able to extend an Objective-C class in Swift

Question

I am using Swift 3.0 on Xcode 8.0 beta. I have installed a library using pods (FMDB) and now I am trying to extend one of its class in swift. I am able to use the API from my extended class but it crashes at runtime.

-[FMResultSet polygonsForColumnIndex:]: unrecognized selector sent to instance 0x608000056890

Below is the code for the extension:

public extension FMResultSet {

    public func polygons(forColumnIndex index: Int32) -> [NMAMapPolygon] {

It crashes here when called:

let rs = db.executeQuery("select AsGeoJSON(geometry) from COM262_Project", withArgumentsIn: nil)
        while (rs?.next())! {

            //Crashes here!
            let polygons = rs?.polygons(forColumnIndex: 0)    
        }

Note : Extensions work for other libraries like Alamofire.

Answer 1

Have you tried setting the function as @objc eg

public extension FMResultSet {
    @objc public func polygons(forColumnIndex index: Int32) -> [NMAMapPolygon] {

On top of that have you changed the build setting Enable Modules to Yes .. Or if your using a config file CLANG_ENABLE_MODULES = YES