Creating a one to many polymorphic relationship with doctrine

Question

Let me start by outlining the scenario. I have a Note object that can be assigned to many different objects

• A Book can have one or moreNot

Answer 1

I add another answer after reading your question once more and realizing that you stated "I want to avoid adding another join table".

Make a Note base entity and extend this class in 3 different note entities for example: BookNote, AddressNote and ImageNote. In my solution the note table would look like this:

id | address_id | book_id | image_id | object_type | content      | date
1  | null       | null    | 1        | image       | "lovely pic" | 2015-02-10
2  | null       | null    | 1        | image       | "red tint"   | 2015-02-30
3  | 1          | null    | null     | address     | "invalid"    | 2015-01-05
4  | null       | 2       | null     | book        | "boobies"    | 2014-09-06
5  | null       | 1       | null     | book        | "prettygood" | 2016-05-05

You cannot use one common column object_id because of the foreign key constraints.

A NotesTrait with setters and getters for notes to prevent code duplication:

notes[] = $note;

        return $this;
    }

    /**
     * Add notes.
     *
     * @param Collection $notes
     * @return self
     */
    public function addNotes(Collection $notes)
    {
        foreach ($notes as $note) {
            $this->addNote($note);
        }
        return $this;
    }

    /**
     * Remove note.
     *
     * @param Note $note
     */
    public function removeNote(Note $note)
    {
        $this->notes->removeElement($note);
    }

    /**
     * Remove notes.
     *
     * @param Collection $notes
     * @return self
     */
    public function removeNotes(Collection $notes)
    {
        foreach ($notes as $note) {
            $this->removeNote($note);
        }
        return $this;
    }

    /**
     * Get notes.
     *
     * @return Collection
     */
    public function getNotes()
    {
        return $this->notes;
    }
}

Your Note entity:

Your BookNote entity:

Your AddressNote entity:

Your ImageNote entity:

Your Book entity:

notes = new ArrayCollection();
    }
}

Your Address entity:

notes = new ArrayCollection();
    }
}

Your Image entity:

notes = new ArrayCollection();
    }
}