Merge pull request #9556 from senny/strong_params_examples

strong parameters example for default values using `fetch`.

1 files changed, 21 insertions, 0 deletions

diff --git a/guides/source/action_controller_overview.md b/guides/source/action_controller_overview.md
index e65f7e5b18..61eb2ef089 100644
--- a/guides/source/action_controller_overview.md
+++ b/guides/source/action_controller_overview.md
@@ -269,6 +269,27 @@ permitted scalar values allowed), a `hobbies` attribute as an array of
 permitted scalar values, and a `family` attribute which is restricted
 to having a `name` (any permitted scalar values allowed, too).
 
+#### More Examples
+
+You want to also use the permitted attributes in the `new`
+action. This raises the problem that you can't use `require` on the
+root-key because normally it does not exist when calling `new`:
+
+```ruby
+# using `fetch` you can supply a default and use
+# the Strong Parameters API from there.
+params.fetch(blog:, {}).permit(:title, :author)
+```
+
+`accepts_nested_attributes_for` allows you update and destroy the
+associated records. This is based on the `id` and `_destroy`
+parameters:
+
+```ruby
+# permit :id and :_destroy
+params.require(:author).permit(:name, books_attributes: [:title, :id, :_destroy])
+```
+
 #### Outside the Scope of Strong Parameters
 
 The strong parameter API was designed with the most common use cases