为什么 Rails 隐藏了 id 列的存在? [英] Why Rails hides the existence of id column?

问题描述

我不太明白需要在 Rails 中隐藏 id 列的存在.它既不会反映在 migration 文件中，也不会反映在 schema.rb 文件中.新手无法知道名为 id 的列已被默认创建为 primary key 的事实.除非他们去检查数据库中表的实际模式(rails dbconsole).

I don't quite understand the need to hide the existence of id column in Rails. It is neither reflected in migration file nor the schema.rb file. There is no way for a newbie to know for the fact that a column named id has been created by default as a primary key. Unless they go and check the actual schema of the table in database (rails dbconsole).

我可以看到迁移文件中默认包含的 timestamps 宏以及 schema.rb 中的两个字段 created_at 和 <代码>updated_at.在这里，开发人员至少得到了一个线索.Rails 也可以为 id 列做同样的事情.但事实并非如此.

I can see the timestamps macro included by default in the migration file as well as in schema.rb as two fields created_at and updated_at. Here, a developer at least gets a clue. Rails could have done the same for id column too. But it doesn't.

为什么要对 id 列保密?它是著名的convention over configuration 的一部分吗?还是所有 MVC 框架的规范?

Why the secrecy around id column? Is it a part of the famous convention over configuration? Or is it a norm across all MVC frameworks?

推荐答案

在数据库设计中，人们普遍认为数字 id 是首选，因为

In database design it is generally accepted that numeric id's are preferred, because

• 它们更容易索引，因此在创建链接(外键)时更容易关注"或检查.
• 在编辑/更新记录时，您有一个唯一(且有效)的标识符

因此，建议始终为所有表格提供唯一的数字键.

So therefore it is advised to give all tables a unique numeric key, always.

现在这个数字键对您的应用程序没有任何意义，它是您的数据库层的实现细节".还要确保每个表都有一个 ID，除非您明确要求不要这样做.

Now this numeric key has no meaning whatsoever to your application, it is a "implementation detail" of your database layer. Also to make sure every table has an id, unless you explicitly ask not to.

我认为这确实属于约定优于配置"的说法:如果每个表都应该有一个 id，为什么还要为每个表明确指定一个 id.

I think this would indeed fall under the "convention over configuration" nomer: why explicitly specify an id for each table if you each table should have one.

时间戳不同:这对某些表很有趣，但对于相同的表，它根本不重要.这也取决于您的应用程序.

The timestamps is different: this is interesting for some tables, but for same tables it is not important at all. It also depends on your application.

请注意，这与 MVC 完全无关.MVC 中的 M 是数据的容器，但在 MVC 中，模型如何填充实际上并不重要.换句话说:ORM 部分不是 MVC 的一部分.您会看到在大多数 MVC 实现中没有 ORM，或者绝对不像与 Rails 那样紧密集成.

Note that this is not at all related to MVC. The M in MVC is a container for data, but in MVC it is actually not really important how the Model gets filled. In other words: the ORM part is not part of MVC. You will see that in most MVC implementations there is no ORM, or definitely not as tightly integrated as with Rails.

简而言之:恕我直言，从迁移中省略id"并不是什么秘密，它只是为了让生活更轻松，为您节省更多的输入时间，并且它确保您遵循一个好的除非您明确不想想要，否则约定俗成.

So in short: imho ommitting the 'id' from the migration is not a secret, it is just to make life easier, saves you some more typing, and it makes sure you follow a good convention unless you explicitly do not want to.

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