61 lines
2.7 KiB
ReStructuredText
61 lines
2.7 KiB
ReStructuredText
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Association Updates: Owning Side and Inverse Side
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=================================================
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When mapping bidirectional associations it is important to
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understand the concept of the owning and inverse sides. The
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following general rules apply:
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- Relationships may be bidirectional or unidirectional.
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- A bidirectional relationship has both an owning side and an inverse side
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- A unidirectional relationship only has an owning side.
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- Doctrine will **only** check the owning side of an assocation for changes.
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Bidirectional Associations
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--------------------------
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The following rules apply to **bidirectional** associations:
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- The inverse side has to use the ``mappedBy`` attribute of the OneToOne,
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OneToMany, or ManyToMany mapping declaration. The mappedBy
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attribute contains the name of the association-field on the owning side.
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- The owning side has to use the ``inversedBy`` attribute of the
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OneToOne, ManyToOne, or ManyToMany mapping declaration.
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The inversedBy attribute contains the name of the association-field
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on the inverse-side.
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- ManyToOne is always the owning side of a bidirectional assocation.
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- OneToMany is always the inverse side of a bidirectional assocation.
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- The owning side of a OneToOne assocation is the entity with the table
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containing the foreign key.
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- You can pick the owning side of a many-to-many assocation yourself.
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Important concepts
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------------------
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**Doctrine will only check the owning side of an assocation for changes.**
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To fully understand this, remember how bidirectional associations
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are maintained in the object world. There are 2 references on each
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side of the association and these 2 references both represent the
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same association but can change independently of one another. Of
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course, in a correct application the semantics of the bidirectional
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association are properly maintained by the application developer
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(that's his responsibility). Doctrine needs to know which of these
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two in-memory references is the one that should be persisted and
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which not. This is what the owning/inverse concept is mainly used
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for.
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**Changes made only to the inverse side of an association are ignored. Make sure to update both sides of a bidirectional association (or at least the owning side, from Doctrine's point of view)**
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The owning side of a bidirectional association is the side Doctrine
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"looks at" when determining the state of the association, and
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consequently whether there is anything to do to update the
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association in the database.
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.. note::
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"Owning side" and "inverse side" are technical concepts of
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the ORM technology, not concepts of your domain model. What you
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consider as the owning side in your domain model can be different
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from what the owning side is for Doctrine. These are unrelated.
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