geraldcroes

val parserFactory = StandardFileParserFactory()
val fileParser = parserFactory.createFromFileName(“filename.xml”)

geraldcroes

class CompanionObjectFileParserFactory {
    companion object : FileParserFactory{
        override fun createFromFileName(fileName: String) =
                when (fileName.substringAfterLast('.')) {
                    "xml" -> XmlFileParser()
                    "json" -> JsonFileParser()
                    else -> throw Exception("I don't know how to deal with $fileName.")
                }
    }
}

geraldcroes

MyFileParserFactory.createFromFileName("filename.json")

geraldcroes

class CompanionObjectFileParserFactory : FileParserFactory {
    companion object : FileParserFactory{
        override fun createFromFileName(fileName: String) =
                when (fileName.substringAfterLast('.')) {
                    "xml" -> XmlFileParser()
                    "json" -> JsonFileParser()
                    else -> throw Exception("I don't know how to deal with $fileName.")
                }
    }
    /* needed if you want to be able to call the createFromFileName from an instance */

geraldcroes

object ObjectFileParserFactory : FileParserFactory {
    override fun createFromFileName(fileName: String) =
            when (fileName.substringAfterLast('.')) {
                "xml" -> XmlFileParser()
                "json" -> JsonFileParser()
                else -> throw Exception("I don't know how to deal with $fileName.")
            }
}

geraldcroes

//Works…
ObjectFileParserFactory.createFromFileName("filename.foo")
 
//...and this still works
val fileParser = ObjectFileParserFactory
fileParser.createFromFileName("filename.json")

geraldcroes

interface FileParser {
    companion object {
       	fun createFromFileName(fileName: String) =
            when (fileName.substringAfterLast('.')) {
                "xml" -> XmlFileParser()
                "json" -> JsonFileParser()
                else -> throw Exception("I don't know how to deal with $fileName.")
            }
    }
}

geraldcroes

FileParser.createFromFile("filename.json")

geraldcroes

fun FileParser.Companion.fromFile(filename: String) = 
        this.createFromFileName(filename)

geraldcroes

val parser = FileParser fromFile "filename.json"