> For the complete documentation index, see [llms.txt](https://kelby.gitbook.io/rails-beginner-s-guide/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://kelby.gitbook.io/rails-beginner-s-guide/activerecord_association_achitecture/association_others/association_relation.md).

# Association Relation

针对 Scope `merge` 操作的实现：

```ruby
# 可以被重写(ThroughAssociation 里就这么做)
def target_scope
  AssociationRelation.create(klass, klass.arel_table, klass.predicate_builder, self).merge!(klass.all)
end
```