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| -rw-r--r-- | guides/source/association_basics.md | 6 |
1 files changed, 6 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: |