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-rw-r--r--guides/source/association_basics.md6
-rw-r--r--guides/source/engines.md8
2 files changed, 14 insertions, 0 deletions
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md
index 9b80a65a44..e133e71d42 100644
--- a/guides/source/association_basics.md
+++ b/guides/source/association_basics.md
@@ -1137,6 +1137,12 @@ Controls what happens to the associated object when its owner is destroyed:
* `:restrict_with_exception` causes an exception to be raised if there is an associated record
* `:restrict_with_error` causes an error to be added to the owner if there is an associated object
+It's necessary not to set or leave `:nullify` option for those associations
+that have `NOT NULL` database constraints. If you don't set `dependent` to
+destroy such associations you won't be able to change the associated object
+because initial associated object foreign key will be set to unallowed `NULL`
+value.
+
##### `:foreign_key`
By convention, Rails assumes that the column used to hold the foreign key on the other model is the name of this model with the suffix `_id` added. The `:foreign_key` option lets you set the name of the foreign key directly:
diff --git a/guides/source/engines.md b/guides/source/engines.md
index a77be917a2..9106b6382d 100644
--- a/guides/source/engines.md
+++ b/guides/source/engines.md
@@ -525,6 +525,14 @@ First, the `author_name` text field needs to be added to the `app/views/blorgh/p
</div>
```
+Next, we need to update our `Blorgh::PostController#post_params` method to permit the new form parameter:
+
+```ruby
+def post_params
+ params.require(:post).permit(:title, :text, :author_name)
+end
+```
+
The `Blorgh::Post` model should then have some code to convert the `author_name` field into an actual `User` object and associate it as that post's `author` before the post is saved. It will also need to have an `attr_accessor` setup for this field so that the setter and getter methods are defined for it.
To do all this, you'll need to add the `attr_accessor` for `author_name`, the association for the author and the `before_save` call into `app/models/blorgh/post.rb`. The `author` association will be hard-coded to the `User` class for the time being.