问题描述
与ActiveRecord的自动分配的挣扎：id属性的，即使它是一个单独的列的主键。
Struggling with ActiveRecord auto assigning the :id attribute as the primary key even though it is a separate column.
Table - legacy-table
id - int
pk_id - int (primary key)
name - varchar2
info - varchar2
型号
class LegacyModel < ActiveRecord::Base
self.table_name = 'legacy-table'
self.primary_key = 'pk_id'
default_scope {order(:name => :asc)}
alias_attribute :other_id, :id
end
我不关心ActiveRecord的自动分配的主键（pk_id）到：但是，我失去所有进入实际ID列id属性。尝试使用别名只是指向我回到了主键。
I don't care that ActiveRecord automatically assigns the primary key (pk_id) to the :id attribute however I lose all access to the actual id column. Trying to use the alias simply points me back at the primary key.
不过注意，该问题是，从该视图我可以使用@legacymodel访问ID列[：ID]。但是，再次调用@ legacymodel.id时，我得到了pk_id列的值。我想要的是能够调用@ legacymodel.other_id并使其指向id列。相反@ legacymodel.service_id，@ legacymodel.id，和@ legacymodel.pk_id都指向同一列pk_id
However one caveat to this issues is that from the view i can access the id column by using @legacymodel[:id]. But again when calling @legacymodel.id I get the value of the pk_id column. What i want is to be able to call @legacymodel.other_id and have it point to the id column. Instead @legacymodel.service_id, @legacymodel.id, and @legacymodel.pk_id all point to the same column pk_id
请注意，这是一个传统的数据库，并修改列是出了问题。我使用Rails 4的MySQL。
Please note that this is a legacy db and modifying the columns are out of the question. I am using Rails 4 with MySql.
反正有没有解决这个code？为什么@legacymodel [：ID]给我不同的结果，然后@ legacymodel.id？
Is there anyway to code around this? Why does @legacymodel[:id] give me different results then @legacymodel.id?
推荐答案
的 read_attribute 方法将读取值了 @属性散的。该 [] 方法使用 read_attribute 。因此， @legacymodel [：ID] 得到 id的值列
The read_attribute method will read a value out of the @attributes hash. The [] method uses read_attribute. So @legacymodel[:id] gets the value of the id column.
的 write_attribute 方法总是试图翻译 ID 到主键的名称......
The write_attribute method always tries to translate id into the name of the primary key...
# ActiveRecord::AttributeMethods::Write
def write_attribute(attr_name, value)
attr_name = attr_name.to_s
attr_name = self.class.primary_key if attr_name == 'id' && self.class.primary_key
...和 [] = 方法使用 write_attribute 。因此， @legacymodel [：ID =＆LT;价值＆GT; 将值设置到主键列， pk_id 。
...and the []= method uses write_attribute. So @legacymodel[:id] = <value> will set a value into the primary key column, pk_id.
的 ID 方法是别名 primary_key 这里的特殊方法：
The id method is a special method that is aliased to the primary_key here:
# ActiveRecord::AttributeMethods::PrimaryKey
if attr_name == primary_key && attr_name != 'id'
generated_attribute_methods.send(:alias_method, :id, primary_key)
end
所以 @ legacymodel.id 将获得 pk_id 列的值。
如果你只想读 ID 到 @ legacymodel.other_id ，那么你可以定义一个方法列这样的：
If you just want to read the id column through @legacymodel.other_id, then you could define a method like:
# LegacyModel class
def other_id
self[:id]
end
但是，如果你还需要通过 @ legacymodel.other_id = 写入 ID 列，那么你可能需要设法找到一种安全的方式来覆盖 write_attribute 方法，这样就可以解决的名称= self.class.primary_key如果attr_name == '身份证'和;＆安培; self.class.primary_key 语句。
But if you also need to write to the id column through @legacymodel.other_id=, then you might need to try to find a safe way to override the write_attribute method so that you can work around the attr_name = self.class.primary_key if attr_name == 'id' && self.class.primary_key statement.
这篇关于导轨的ActiveRecord处理一个ID列不是主键的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！