Question

我的CommercialDocument模型具有discount_amount属性和discount_amount_with_tax虚拟属性。

以下是我在模型中定义的方法：

def discount_amount_with_tax
  discount_amount * (1 + tax.rate / 100)
end

def discount_amount_with_tax=(amount)
  self.discount_amount = amount.to_f / (1 + tax.rate / 100)
end

在我的表单中，用户可以同时填写discount_amount和discount_amount_tax：

= f.label :discount_amount
= f.text_field :discount_amount
= f.text_field :discount_amount_with_tax

我想优先考虑discount_amount_with_tax字段，这意味着除非另一个字段为空，否则不得考虑discount_amount。

我的问题是，如果我在discount_amount_with_tax字段中没有放任何内容，让我们在discount_amount中说10，那么discount_amount将等于0，这显然不是我想要的

我该如何解决这个问题？

非常感谢任何帮助。

Answer 1

"".to_i
# => 0

空字符串转换为零整数。因此：

def discount_amount_with_tax=(amount)
  self.discount_amount = amount.to_f / (1 + tax.rate / 100)
end

# same as...

def discount_amount_with_tax=(0)
  self.discount_amount = 0 / (...)
end

# 0 / anything except zero = 0
# self.discount_amount = 0 no matter what

在批量分配期间，调用discount_amount_with_tax=。空白表单输入作为空字符串传递，然后Active Record将转换为整数（零）。无论discount_amount_with_tax=以前的值是什么，discount_amount都会将discount_amount设置为零。

简单来说就是使用条件：

def discount_amount_with_tax=(amount)
  self.discount_amount = (amount.to_f / (1 + tax.rate / 100)) if amount > 0
end

请注意，这是简单方法，而非理想方式。更好的解决方案是在控制器中编写自定义设置器逻辑，而不是质量分配;基本上手动在控制器中设置这些属性。

Answer 2

我认为您可以在此处使用before_validation回调来设置discount_amount字段。

  before_validation :calculate_discount_amount

  def discount_amount_with_tax
    @discount_amount_with_tax ||= discount_amount * (1 + tax.rate / 100.0)
  end

  def discount_amount_with_tax=(amt)
    @discount_amount_with_tax = amt
  end

  def calculate_discount_amount
    self.discount_amount = discount_amount_with_tax / (1 + tax.rate / 100.0)
  end

提醒你需要使用100.0而不是100，这样你就可以用浮点而不是整数来划分。

选择要提交的表单字段

2 个答案: