Rails：创建自定义数据类型/创建简写 [英] Rails: creating a custom data type / creating a shorthand

问题描述

我想知道如何创建自定义数据类型以在rake迁移文件中使用。示例：如果要创建模型，则可以在迁移文件内添加列。可能看起来像这样：

I am wondering how I could create a custom data type to use within the rake migration file. Example: if you would be creating a model, inside the migration file you can add columns. It could look like this:

  def self.up
    create_table :products do |t|
      t.column :name, :string
      t.timestamps
    end
  end

我想知道如何创建这样的东西：

I would like to know how to create something like this:

t.column :name, :my_custom_data_type

创建例如 currency类型的原因，无非一个小数，精度为8，小数位数为2。由于我仅使用MySQL，因此该数据库的解决方案就足够了。

The reason for this to create for example a "currency" type, which is nothing more than a decimal with a precision of 8 and a scale of 2. Since I use only MySQL, the solution for this database is sufficient enough.

感谢您的反馈和意见！

推荐答案

您想要做的是定义一个新的列创建方法，该方法提供用于创建自定义类型的选项。从本质上讲，这是通过添加在迁移中行为类似于 t.integer ... 的方法来完成的。技巧是弄清楚将代码添加到何处。

What you're looking to do is define a new column creation method that provides the options to create your custom type. Which is essentially done by adding a method that behaves like t.integer ... in migrations. The trick is figuring out where to add that code.

在初始化器目录中的某些位置应放置以下代码段：

Some where in your initializers directory place this snippet of code:

module ActiveRecord::ConnectionAdapters
  class TableDefinition
    def currency (*args)
      options = args.extract_options!
      column_names = args
      options[:precision] ||= 8
      options[:scale] ||= 2
      column_names.each { |name| column(name, 'decimal', options) }
    end                                                                     
  end
end

现在您可以使用货币方法在需要时随时定义货币列。

Now you can use the currency method do define a currency column any time you need it.

示例：

def self.up
  create_table :products do |t|
    t.currency :cost
    t.timestamps
  end
end

要将货币列添加到现有表中：

To add a currency column to an existing table:

def self.up
  change_table :products do |t|
    t.currency :sell_price
  end
end   

注意：我还没有时间进行测试，因此无法保证。如果它不起作用，则至少应该使您走上正确的轨道。

Caveat: I haven't time to test it, so there's no guarantees. If it doesn't work, it should at least put you on the right track.

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