Cakephp 3, Saving form data on association tables - cakephp

Question

Trying to set up an example on how to use join table with extra data I have the following set:
table students: id, name, [...]
table courses: id, title, [...]
join table courses_students: id, course_id, student_id, grade, hours_attended
The two base table's :
class StudentsTable extends Table {
public function initialize(array $config) {
$this->belongsToMany('Courses', [
'alias' => 'Courses',
'foreignKey' => 'student_id',
'targetForeignKey' => 'course_id',
'joinTable' => 'courses_students',
'through' => 'CoursesStudents',
]);
}
class CoursesTable extends Table {
public function initialize(array $config) {
$this->belongsToMany('Students', [
'alias' => 'Students',
'foreignKey' => 'course_id',
'targetForeignKey' => 'student_id',
'joinTable' => 'courses_students',
'through' => 'CoursesStudents',
]);
}
And the association table:
class CoursesStudentsTable extends Table {
public function initialize(array $config) {
$this->belongsTo('Courses', [
'alias' => 'Courses',
'foreignKey' => 'course_id'
]);
$this->belongsTo('Students', [
'alias' => 'Students',
'foreignKey' => 'student_id'
]);
}
Having some courses available in the table, I try to add and edit student records. Setting
[courses] => [_ids]
in the student record creates the records in both students table and the association table.
How should the post data array be formed in order to be able to store the grade and hours_attended fields in the association table when saving the student record?

Answer 1

You should configure your form field as the following assuming you are in the Courses form.
echo $this->Form->create($courses);
echo $this->Form->input("Courses.id");
echo $this->Form->input("Courses.title");
echo $this->Form->input("Courses.courses_students.$i.grade");
echo $this->Form->input("Courses.courses_students.$i.hours_attended");
The basic idea is that your forms should exactly follow how the data is formatted when retrieved in your controller.
This will then format your data correctly for you.
Then in your controller, you'll need to pass the associations to patch your entity.
$courses = $this->Courses->patchEntity($this->request->data(), ['associations' => ['CoursesStudents']]);
This will merge your associated request data in your entity, so you can save it.