Yii question about relations function in AR Model, many to one relationship.

Question

So here's the scenario:

I have two table, Issue & Project.

A Project can have many Issue and an Issue can exactly one project.

Since Issue is many to one, do you have to define it?

Cause I know in Project Model I have:

public function relations()
{
    return array(
    'issues' => array(self::HAS_MANY, 'Issue', 'project_id'),
    'users' => array(self::MANY_MANY, 'User', 'tbl_project_user_assignment(project_id, user_id)'),
    );
}

For Issue Model I have nothing but foreign keys:

public function relations()
{
    // NOTE: you may need to adjust the relation name and the related
    // class name for the relations automatically generated below.
    return array(
        'requester' => array(self::BELONGS_TO, 'User', 'requester_id'),
        'owner' => array(self::BELONGS_TO, 'User', 'owner_id'),
        'project' => array(self::BELONGS_TO, 'Project', 'project_id'),
    );
}

I'm guessing anything to one relationship does not need to be define?

Thank you in advance.

BTW, I'm doing agile Yii book and I ended up asking myself this question. There's a has-one option in AR class (http://www.yiiframework.com/doc/guide/database.arr).

But is this case optional for some reason?

Answer 1

In your Issue model you already have the relation specified as BELONGS_TO the project model.

I also just got the new yii-book. It helped me alot!

Happy coding :)

Answer 2

It helps me to think of the difference between BELONGS_TO and HAS_ONE as "where is the foreign key stored"? If the Project model stored "Issue_Id" then potentially Issue could have many Projects. You use the HAS_ONE relationship to state that even if Issue COULD have many projects, it only has ONE.

*However, the more common case is if you are storing the Project_Id in the Issue model (and I assume you are). Then you have to use the BELONGS_TO relationship.* It appears you have defined the relationships correctly above.

Someone posted a similar question relating to Yii relations here that I helped answer: http://stackoverflow.com/questions/3309084/yii-using-relation-has-one-to-get-data-from-the-related-table-to-display-in-lis/

As to your concern about "needing" to define relationships, you don't "need" to define any. You could write your own SQL queries to do the same thing. The ActiveRecord relations are just a convenience thing to make querying for related records simpler. If you are never going to look up an Issue's Project, then you don't "need" to define the "project" BELONGS_TO relationship.

Without actually seeing your database structure it looks to me like you have everything set up correctly. You can now easily make both $issue->project and $project->issues "lazy" relational queries, taking full advantage of the power of the Relational Active Record. Cheers and good luck with project!