使空白参数[] nil [英] Make blank params[] nil

问题描述

当用户提交表单并将某些字段留空时，它们将在DB中保存为空白。我想遍历params [：user]集合（例如），如果一个字段为空，在更新属性之前将其设置为nil。我不知道该怎么做，虽然作为我知道迭代创建新对象的唯一方式：

When a user submits a form and leaves certain fields blank, they get saved as blank in the DB. I would like to iterate through the params[:user] collection (for example) and if a field is blank, set it to nil before updating attributes. I can't figure out how to do this though as the only way I know to iterate creates new objects:

coll = params[:user].each do |c|
    if c == ""
       c = nil
    end
end

感谢。

推荐答案

通过在控制器中使用过滤器来影响模型保存或更新时的行为。我认为一个更清洁的方法将是一个 before_save 回调在模型或观察者。这样，无论是通过控制器，控制台还是运行批处理过程，您都会得到相同的行为。

Consider what you're doing here by using filters in the controller to affect how a model behaves when saved or updated. I think a much cleaner method would be a before_save call back in the model or an observer. This way, you're getting the same behavior no matter where the change originates from, whether its via a controller, the console or even when running batch processes.

示例：

class Customer < ActiveRecord::Base
  NULL_ATTRS = %w( middle_name )
  before_save :nil_if_blank

  protected

  def nil_if_blank
    NULL_ATTRS.each { |attr| self[attr] = nil if self[attr].blank? }
  end
end

这会产生预期的行为：

>> c = Customer.new
=> #<Customer id: nil, first_name: nil, middle_name: nil, last_name: nil>
>> c.first_name = "Matt"
=> "Matt"
>> c.middle_name = "" # blank string here
=> ""
>> c.last_name = "Haley"
=> "Haley"
>> c.save
=> true
>> c.middle_name.nil?
=> true
>>

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