type AppController struct {
  *rev.Controller
}

type Controller struct {
    Name       string
    Type       *ControllerType
    MethodType *MethodType

    Request  *Request
    Response *Response

    Flash      Flash                  // User cookie, cleared after each request.
    Session    Session                // Session, stored in cookie, signed.
    Params     Params                 // Parameters from URL and form (including multipart).
    Args       map[string]interface{} // Per-request scratch space.
    RenderArgs map[string]interface{} // Args passed to the template.
    Validation *Validation            // Data validation helpers
    Txn        *sql.Tx                // Nil by default, but may be used by the app / plugins
}

// Flash represents a cookie that gets overwritten on each request.
// It allows data to be stored across one page at a time.
// This is commonly used to implement success or error messages.
// e.g. the Post/Redirect/Get pattern: http://en.wikipedia.org/wiki/Post/Redirect/Get
type Flash struct {
    Data, Out map[string]string
}

// These provide a unified view of the request params.
// Includes:
// - URL query string
// - Form values
// - File uploads
type Params struct {
    url.Values
    Files map[string][]*multipart.FileHeader
}

// A signed cookie (and thus limited to 4kb in size).
// Restriction: Keys may not have a colon in them.
type Session map[string]string

type Request struct {
    *http.Request
    ContentType string
}

type Response struct {
    Status      int
    ContentType string
    Headers     http.Header
    Cookies     []*http.Cookie

    Out http.ResponseWriter
}

func (c AppController) ShowLogin(username string) rev.Result {
    ..
    return c.Render(username)
}

type Result interface {
    Apply(req *Request, resp *Response)
}