gistfile1.swift

class Hoge{
    init(){
        println("Hoge")
    }
}

class Fuga{
    init(){
        println("Fuga")
    }
}

class Homu{
    init(){
        println("Homu")
    }
}

class JSONResponse{

    var responseString : String? = nil

    func responseObject() -> String?
    {
        return responseString
    }
    
}

extension JSONResponse{
    func responseObject() -> Hoge?
    {
        var response:String? = self.responseObject()
        return Hoge()
    }
}

extension JSONResponse{
    func responseObject() -> Fuga?
    {
        return Fuga()
    }
}
extension JSONResponse{
    func responseObject() -> Homu?
    {
        return Homu()
    }
}

var response = JSONResponse()
var hoge:Hoge? = response.responseObject()
var fuga:Fuga? = response.responseObject()
var homu:Homu? = response.responseObject()