Rails 生成 has_many 关联 [英] Rails generate has_many association

问题描述

有没有办法在控制台中使用 Rails generate scaffold 命令为列生成 has_many 关联?

Is there a way to generate has_many association for a column using Rails generate scaffold command in the console?

我知道 belongs_to 可用，并且有 references 的用例，但不确定 has_many

I know belongs_to is available and there are use cases of references but not sure of has_many

推荐答案

has_many 关系没有列.belongs_to 由包含外键的列支持.

There is no column for a has_many relationship. A belongs_to is backed by a column which holds a foreign key.

所以如果你生成一个脚手架:rails g scaffold Post

So if you generate a scaffold: rails g scaffold Post

然后你生成另一个脚手架:rails g scaffold Comment post:references

And then you generate another scaffold: rails g scaffold Comment post:references

然后 rails 将创建一个迁移，将名为 post_id 的列添加到 Comment 表并在其上创建索引.对于这两个表，它在 comments(post_id) 和 posts(id) 之间创建外键约束.Rails 还将在 Comment 模型中添加 belongs_to :post.

Then rails will create a migration that adds a column named post_id to the Comment table and creates an index on it. For both tables, it creates foreign key constraints between comments(post_id) and posts(id). Rails will also add belongs_to :post in the Comment model.

您可以随时向模型添加 has_many，只要另一个模型 belongs_to 第一个模型并且具有外键列的迁移.

At anytime you can add a has_many to a model as long as another model belongs_to the first model and has a migration with the foreign key column.

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