views.go

//...
func (c *controller) vote(ctx context.Context, request *web.Request) web.Result {
	questionID, err := strconv.Atoi(request.Params["question_id"])
	if err != nil {
		return c.responder.ServerError(err)
	}
	var question Question
	if c.db.Preload("Choices").First(&question, questionID).RecordNotFound() {
		return c.responder.NotFound(gorm.ErrRecordNotFound)
	}
	var choice Choice
	choiceIDstr, err := request.Form1("choice")
	if err != nil {
		return c.noSelectedChoice(question)
	}
	choiceID, err := strconv.Atoi(choiceIDstr)
	if err != nil {
		return c.noSelectedChoice(question)
	}
	for _, c := range question.Choices {
		if c.ID == uint(choiceID) {
			choice = c
			break
		}
	}
	if choice.ID == 0 {
		return c.noSelectedChoice(question)
	}
	choice.Votes++
	c.db.Save(&choice)
	return c.responder.RouteRedirect("results", map[string]string{"question_id": strconv.Itoa(questionID)})
}
func (c *controller) noSelectedChoice(question Question) web.Result {
	var viewData struct {
		Question     Question
		ErrorMessage string
	}
	viewData.Question = question
	viewData.ErrorMessage = "You didn't select a choice."
	return c.responder.Render("detail", viewData)
}