Rails 5的ActiveRecord :: Migration中的[5.0]是什么意思? [英] What’s does the [5.0] in Rails 5’s ActiveRecord::Migration mean?
问题描述
我在Rails 5应用程序中创建的迁移已将 5.0
传递给方法:
A migration I created in a Rails 5 application had 5.0
passed into a method:
class CreateVariableKeys < ActiveRecord::Migration[5.0]
...
end
我会想知道 [5.0]
是什么意思。
I would like to know what the [5.0]
means.
推荐答案
它是 ActiveRecord :: Migration
的类方法,并已定义为此处。
It is a class method of ActiveRecord::Migration
and is defined here.
它允许我们在 4.2之间选择希望使用的迁移版本。
和 5.0
。该方法抛出:
It allows us to select the version of migrations we wish to use between 4.2
and 5.0
. The method throws a:
未知的迁移版本...
"Unknown migration version ... "
如果将不兼容的版本作为参数传递,则出错。
error if an incompatible version is passed as an argument.
ActiveRecord $ c $的可用于生产的版本c>没有该方法,因此 Rails 5 超出beta时应消失。
Production ready versions of ActiveRecord
don’t have that method so it should go away as soon as Rails 5 goes out of beta.
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