Usage example for Result<T> in Swift

Result type usage

        var key : String?
        let res = getPathComponents( file )
            >>= { (let components ) -> Result<FileTypes> in
                key = components.filenameWithoutExt
                return FileTypes.fromExt( components.ext )
            }
            >>= { (let type ) -> Result<Void> in
                switch type {
                case .Video, .Image:
                    var caption : String?
                    switch( resourcesByName[key!] ) {
                    case .Some(.CaptionFile( let c )):
                        caption = c
                    case .Some(.MediaFile(_)):
                        return .Fail("multiple media files with the same name" );
                    case .None:
                        break;
                    }
                    let r = Resource( type: Resource.Types( type ), filename: file, caption: caption )
                    resourcesByName[key!] = MediaOrCaption.MediaFile( r )

                case .Text:
                    let mf = resourcesByName[key!]
                    switch( mf ) {
                    case .Some(.CaptionFile(_)):
                        return .Fail( "multiple caption files" );
                    case .Some(.MediaFile( var r )):
                        resourcesByName[key!] = MediaOrCaption.MediaFile( Resource( type: r.type, filename: r.filename, caption: file ) )
                    case .None:
                        resourcesByName[key!] = MediaOrCaption.CaptionFile( file )
                    }
                }
                return .Ok( Box<Void>() )
            }

Uses https://gist.github.com/philsquared/1d267d823130eaf7641a