ActiveRecord - 验证 :allow_blank 始终处于活动状态，即使它具有 :unless

Question

我有这个模型

class User < ActiveRecord::Base
  attr_accessible :type, :school_name, :school_grade

  validates :type, :inclusion =>{:in =>['1','2']}, :allow_blank => true
  validates :school_name,  :presence =>{:if => :student?}
  validates :school_grade, :numericality =>{:only_integer =>true}, :allow_blank => {:unless => :student?}

  def student?
    type.to_s == '1'
  end
end

我尝试了以下模式。

User.create(:type =>'2', :school_name =>nil, :school_grade =>nil)

=> 好的。没有发生错误。

User.create(:type =>'1', :school_name =>nil, :school_grade =>1)

=> 好的。发生 ActiveRecord::RecordInvalid 错误“school_name is empty”。

User.create(:type =>'1', :school_name =>'foo', :school_grade =>'string is not a number')

=> 好的。出现验证错误“school_grade 不是数字”。

User.create(:type =>'1', :school_name =>'foo', :school_grade =>nil)

=> 不合格。我预计“school_grade is not a number”错误，但没有发生错误。

我也尝试过这种模式，但得到了相同的结果。

  validates :school_grade, :numericality =>{:only_integer =>true}, :allow_blank => {:if => :not_student?}

  def not_student?
    type.to_s != '1'
  end

我猜验证 :allow_blank 始终处于活动状态，但为什么呢？以及如何解决？

谢谢。

Answer 1

allow_blank 不接受Hash，只接受布尔值，所以你不能写像:allow_blank => {:unless => :student?} 这样的东西，你可以在源代码activemodel-4.1.2/lib/active_model/validator.rb 中看到

def validate(record)
  attributes.each do |attribute|
    value = record.read_attribute_for_validation(attribute)
    next if (value.nil? && options[:allow_nil]) || (value.blank? && options[:allow_blank])
    validate_each(record, attribute, value)
  end
end

但是，您想要实现的目标可以通过两行来完成：

class User < ActiveRecord::Base
  validates_presence_of :school_grade, :if => :student?
  validates :school_grade, :numericality =>{:only_integer =>true}, :allow_blank => true
end

Answer 2

您希望 allow_blank 是有条件的还是整个数值验证？

如果是后者：

validates :school_grade, :numericality =>{:only_integer =>true}, :allow_blank => true, :unless => :student?
validates :school_grade, :numericality =>{:only_integer =>true}, :allow_blank => false, :if => :student?