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Diffstat (limited to 'railties/guides')
-rw-r--r-- | railties/guides/source/active_record_querying.textile | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/railties/guides/source/active_record_querying.textile b/railties/guides/source/active_record_querying.textile index e3871a3c34..3970625c35 100644 --- a/railties/guides/source/active_record_querying.textile +++ b/railties/guides/source/active_record_querying.textile @@ -965,6 +965,47 @@ Using a class method is the preferred way to accept arguments for scopes. These category.posts.1_week_before(time) </ruby> +h4. Working with scopes + +Where a relational object is required, the +scoped+ method may come in handy. This will return an +ActiveRecord::Relation+ object which can have further scoping applied to it afterwards. A place where this may come in handy is on associations + +<ruby> + client = Client.find_by_first_name("Ryan") + orders = client.orders.scoped +</ruby> + +With this new +orders+ object, we are able to ascertain that this object can have more scopes applied to it. For instance, if we wanted to return orders only in the last 30 days at a later point. + +<ruby> + orders.where("created_at > ?", 30.days.ago) +</ruby> + +h4. Applying a default scope + +If we wish for a scope to be applied across all queries to the model we can use the +default_scope+ method within the model itself. + +<ruby> + class Client < ActiveRecord::Base + default_scope where("removed_at IS NULL") + end +</ruby> + +When queries are executed on this model, the SQL query will now look something like this: + +<ruby> + SELECT * FROM clients WHERE removed_at IS NULL +</ruby> + +h4. Removing all scoping + +If we wish to remove scoping for any reason we can use the +unscoped+ method. This is especially useful if a +default_scope+ is specified in the model and should not be applied for this particular query. + +<ruby> + Client.unscoped.all +</ruby> + +This method removes all scoping and will do a normal query on the table. + h3. Dynamic Finders For every field (also known as an attribute) you define in your table, Active Record provides a finder method. If you have a field called +first_name+ on your +Client+ model for example, you get +find_by_first_name+ and +find_all_by_first_name+ for free from Active Record. If you have a +locked+ field on the +Client+ model, you also get +find_by_locked+ and +find_all_by_locked+ methods. |