将布尔值传递给 update_attributes 时出现问题
我有以下模型：
class GuestCatering < ActiveRecord::Base
# Validation
validates :name, :presence => true
validates :order_number, :presence => true
validates :orderable, :presence => true
end
但是当我尝试使用以下代码更新现有的 GuestCatering 时：
guest_catering.update_attributes(:orderable => false)
宾客餐饮变量是有效的 GuestCatering 对象。 guest_catering 对象在更新后出现错误，如下所示：
<{[:orderable, ["can't be blank"]]=>nil}>
但是当我传递 orderable =>; true，一切都很好，没有错误。
这里出了什么问题，为什么我不能将 orderable 设置为 false？
I've got the following Model:
class GuestCatering < ActiveRecord::Base
# Validation
validates :name, :presence => true
validates :order_number, :presence => true
validates :orderable, :presence => true
end
But when I'll try to update an existing GuestCatering with the following code:
guest_catering.update_attributes(:orderable => false)
The guest catering variable is a valid GuestCatering object.
The guest_catering object has errors after the update, like that:
<{[:orderable, ["can't be blank"]]=>nil}>
But when i pass a orderable => true, everything is fine and no errors.
What's wrong here, why can't i set orderable to false?
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评论（3）
通过使用
validates :orderable, :presence => 您的模型实际上表现得完全按照您的指示。 true验证布尔标志是否存在没有什么意义 - 它将是
true、nil或false- 并且在 Ruby 中world、nil 和 false 在布尔逻辑中具有相同的语义值。在内部，
validates :presence依赖于被检查的属性的值，以便在调用blank?时返回false。而且，在 Rails（使用 ActiveSupport）中，false.blank?计算结果为true- 这意味着您的字段未通过验证。只需删除该验证，一切都会按预期进行。
Your model is actually behaving exactly as you told it to, through your use of
validates :orderable, :presence => trueThere's little point validating the presence of a boolean flag - it's going to be
true,nilorfalse- and in Ruby world, nil and false have the same semantic value when it comes to boolean logic.Internally,
validates :presencerelies on the value of the attribute being checked to returnfalsewhenblank?is called. And, in Rails (with ActiveSupport),false.blank?evaluates astrue- which means that your field is failing the validation.Simply remove that validation and everything will work as expected.
就像 Dan Cheail 在他的回答中已经说过的那样，
nil和false布尔值在语义上是相同的。但是，如果您确实需要验证它（不允许
nil），您可以随时执行以下操作：validates_inclusion_of :orderable, :in => [真，假]Like Dan Cheail already said in his answer, a
nilandfalseboolean is semantically the same thing.But, if you really need to validate it (not allowing
nil), you can always do :validates_inclusion_of :orderable, :in => [true, false]而不是
validates :presence =>; :true，您应该使用如下所示的默认值编写迁移：我假设您的默认值应该是
false。如果true，则使用 1 作为默认值。然后它将在数据库中设置默认值。因此，您可以省略验证检查。@dan 回答了您无法使用
validates :presence的原因。存在意味着不为空，Rails 使用.blank?函数来实现此目的，并且false.blank?为trueInstead of
validates :presence => :true, you should write your migrations with the default value like this:I assume your default value should be
false. Iftrue, use 1 as default. Then it will set the default value in database. So, you can omit the validation check.The reason you cannot use
validates :presenceis answered by @dan. Presence means not blank and Rails use.blank?function for this andfalse.blank?istrue