Ruby-on-rails Rails 生成 has_many 关联
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Rails generate has_many association
提问by Passionate Engineer
Is there a way to generate has_many association for a column using Rails generate scaffoldcommand in the console?
有没有办法Rails generate scaffold在控制台中使用命令为列生成 has_many 关联？
I know belongs_tois available and there are use cases of referencesbut not sure of has_many
我知道belongs_to可用，并且有使用案例references但不确定has_many
回答by Alex Peachey
There is no column for a has_manyrelationship. A belongs_tois backed by a column which holds a foreign key.
没has_many有关系列。Abelongs_to由包含外键的列支持。
So if you generate a scaffold: rails g scaffold Post
所以如果你生成一个脚手架： rails g scaffold Post
And then you generate another scaffold: rails g scaffold Comment post:references
然后你生成另一个脚手架： rails g scaffold Comment post:references
Then rails will create a migration that adds a column named post_idto 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 :postin the Comment model.
然后 rails 将创建一个迁移，将一个名为post_idComment 表的列添加到该列并在其上创建一个索引。对于这两个表，它在comments(post_id)和之间创建外键约束posts(id)。Rails 还将添加belongs_to :post到 Comment 模型中。
At anytime you can add a has_manyto a model as long as another model belongs_tothe first model and has a migration with the foreign key column.
您可以随时has_many向模型添加一个，只要另一个模型belongs_to是第一个模型并且具有外键列的迁移。
