如何使用CakePHP3提取关联的belongsToMany实体

Question

I have Users and Courses table with belongsToMany relation. UserTable has

$this->belongsToMany('Courses', [
    'foreignKey' => 'user_id',
    'targetForeignKey' => 'course_id',
    'joinTable' => 'courses_users'
]);

and CoursesTable has

$this->belongsToMany('Users', [
    'foreignKey' => 'course_id',
    'targetForeignKey' => 'user_id',
    'joinTable' => 'courses_users'
]);

Now, I want to fetch courses with user_id. In my CoursesController, I tried

public function myCourses()
{
    $id = $this->Auth->user('id');
    $courses = $this->Courses->find('all',
        ['contain' => ['Users'],
        'condition' => ['Courses.user_id' => $id]
        ]);
    $this->set('courses', $courses);
}

when I debug($courses) with this code, I got '(help)' => 'This is a Query object, to get the results execute or iterate it.' message. I'm searching information and trying to do it for many hours but I can't make it. How can I fetch Courses datas with user_id? Thanks in advance.

Answer 1

If it's a has-and-belongs-to-many (HABTM) association with a join table of courses_users , you shouldn't even have a user_id field in your Courses table.

So now that we've determined you can't do what you were trying ( Courses.user_id ), we can look at what you thought you were trying:

 $courses = $this->Courses->find('all',
     ['contain' => ['Users'],
     //'condition' => ['Courses.user_id' => $id]
 ]);

This says "find all courses and any users that are associated with those courses".

But what you really WANT (I believe) is: "find all courses that belong to this specific user".

To do that, you'll want to use an matching() instead.

According to the CakePHP book :

A fairly common query case with associations is finding records 'matching' specific associated data. For example if you have 'Articles belongsToMany Tags' you will probably want to find Articles that have the CakePHP tag. This is extremely simple to do with the ORM in CakePHP:

$query = $articles->find();
$query->matching('Tags', function ($q) {
    return $q->where(['Tags.name' => 'CakePHP']);
});

So in your case, it would be something like this:

$query = $courses->find();
$query->matching('Users', function ($q) use ($id) {
    return $q->where(['Users.id' => $id]);
});