Question

我希望我的UserPrice模型的属性默认为0（如果它们为空或者它没有验证数值）。这些属性是tax_rate，shipping_cost和price。

class CreateUserPrices < ActiveRecord::Migration
  def self.up
    create_table :user_prices do |t|
      t.decimal :price, :precision => 8, :scale => 2
      t.decimal :tax_rate, :precision => 8, :scale => 2
      t.decimal :shipping_cost, :precision => 8, :scale => 2
    end
  end
end

首先，我将:default => 0放在表格的所有3列中，但我不想这样，因为它已经填写了字段，我想使用占位符。这是我的UserPrice模型：

class UserPrice < ActiveRecord::Base
  attr_accessible :price, :tax_rate, :shipping_cost
  validates_numericality_of :price, :tax_rate, :shipping_cost
  validates_presence_of :price
end

ANSWER

before_validation :default_to_zero_if_necessary, :on => :create

private 

def default_to_zero_if_necessary
    self.price = 0 if self.price.blank?
    self.tax_rate = 0 if self.tax_rate.blank?
    self.shipping_cost = 0 if self.shipping_cost.blank?
end

Answer 1

您可以将其置于before_validation生命周期行动中：

before_validation :default_to_zero_if_necessary

private
  def default_to_zero_if_necessary
    price = 0 if price.blank?
    tax_rate = 0 if tax_rate.blank?
    shipping_cost = 0 if shipping_cost.blank?
  end

您无需检查输入是否为字符串，因为Rails会在该方案中将其默认为0。如果您在create操作期间只需要此验证，则可以将其更改为：

before_validation :default_to_zero_if_necessary, :on => :create

Answer 2

在这种情况下，我可能会设置：default =＆gt; 0，：nil =＆gt; db迁移中为false。

class CreateUserPrices < ActiveRecord::Migration
  def self.up
    create_table :user_prices do |t|
      t.decimal :price, :precision => 8, :scale => 2, :default => 0, :nil => false
      t.decimal :tax_rate, :precision => 8, :scale => 2, :default => 0, :nil => false
      t.decimal :shipping_cost, :precision => 8, :scale => 2, :default => 0, :nil => false
    end
  end
end

我必须使用格式化电话号码https://github.com/mdeering/attribute_normalizer等更高级的内容时使用属性规范化器。属性规范化器非常适合确保数据格式。

# here I format a phone number to MSISDN format (004670000000)
normalize_attribute :phone_number do |value|
  PhoneNumberTools.format(value)
end

# use this (can have weird side effects)
normalize_attribute :price do |value|
  value.to_i
end

# or this.
normalize_attribute :price do |value|
  0 if value.blank?
end

如果空白或未验证数值，则将属性默认设置为0

2 个答案: