为什么删除对 full_messages 函数不起作用？

Question

我有以下代码：

def register_learner
  @event = Event.find(params[:event_id])
  @registation = EventRegistration.new first_name: params[:first_name], last_name: params[:last_name], email: params[:email], event_id: params[:event_id]

  if !@registation.valid?
    @registation.errors.full_messages.delete("Event has already been taken"
    flash[:notice] = @registation.errors.full_messages.to_sentence
    redirect_to(event_path(@event))
  else
    @registation.save
  end
end

请注意 @registation.errors.full_messages.delete("Event has already been taken") 行，我试图从 full_messages 数组中删除此特定消息，但它不起作用。下一行是 flash 消息，消息 "Event has already been taken" 仍在显示。

这是通过控制台进行的健全性检查...

2.1.5 :001 > errors = ["Event has already been taken", "Last name can't be blank"]
 => ["Event has already been taken", "Last name can't be blank"]
2.1.5 :002 > errors.delete "Event has already been taken"
 => "Event has already been taken"
2.1.5 :003 > errors
 => ["Last name can't be blank"]

我错过了什么？

Answer 1

这是因为full_messages是一个方法，每次调用都会生成一个新的数组。做你想做的事：

errors = @registation.errors.full_messages
errors.delete("Event has already been taken")
flash[:notice] = errors.to_sentence

这回答了问题，现在有一个问题 - 你为什么需要这样做？可能有更好的方法。

总的来说，依赖字符串通常不是一个好主意，想象一下，半年后您将需要更改错误消息以进行此验证。你能 100% 确定你也会记得在这里更改它吗？如果没有，你有一个错误。

Answer 2

嗯，因为 Rails 会在您每次调用方法时使用 errors 重新创建 #full_messages：

def full_messages(options = {})
  @errors.values.inject([]) do |full_messages, errors|
    full_messages + errors.map { |error| error.full_message }
  end
end

Source

您可以使用 #select 跳过该消息：

@registation.errors.full_messages.select{|x| x != "Event has already been taken"}.to_sentence

此外，您可以在 #errors.messages 上使用 #delete（而不是 full_messages），因为它们是底层对象的暴露属性（不是副本，与 full_messages):

@registration.errors.messages[:event].delete('has already been taken')

为什么删除对 full_messages 函数不起作用？

Why does delete not work on full_messages function?

validation

ruby-on-rails

ruby-on-rails-3