An addition to atk4/data to easily manage Many To Many (MToM) Relations. The purpose is to write as little code as possible for actual MToM operations.
The project consists of two files:
- JunctionModel: A base model for a junction class (like StudentToLesson). Working descendants can be coded with a few lines of code. Static methods to add (e.g.
StudentToLesson::addMToMRelation($student, $lesson);), remove ((e.g.StudentToLesson::removeMToMRelation($student, $lesson);) and check ((e.g.StudentToLesson::hasMToMRelation($student, $lesson);) are implemented here. - MToMTrait: A Trait which is added to the models to be linked, (like Student and Lesson). With this trait, the MToM relation can be defined with a single line in Model::init():
$this->addMToMReferenceAndDeleteHook();.
The easiest way to use this repository is to add it to your composer.json in the requirement section:
{
"require": {
"philippgrashoff/mtomforatk": "4.0.*"
}
}As example, lets use Students and Lessons. A Student can have many Lessons, a Lesson can have many Students. To map this MToM relationship, 3 classes are created. Demo models for this example can be found in tests\Testmodels:
- Student: A normal model which uses MToMTrait.
- Lesson: A normal model which uses MToMTrait.
- StudentToLesson: The junction model carrying the student_id and lesson_id for each MToM relation between Students and Lessons.
After setting these classes up using this project, MToM operations can be done easily:
<?php declare(strict_types=1);
use Atk4\Data\Persistence\Sql;
use PhilippR\Atk4\MToM\Tests\Testmodels\Lesson;
use PhilippR\Atk4\MToM\Tests\Testmodels\Student;
use PhilippR\Atk4\MToM\Tests\Testmodels\StudentToLesson;
$persistence = new Sql('sqlite::memory:');
$studentHarry = (new Student($persistence))->createEntity();
$studentHarry->set('name', 'Harry');
$studentHarry->save();
$lessonGeography = (new Lesson($persistence))->createEntity();
$lessonGeography->set('name', 'Geography');
$lessonGeography->save();
//now, lets easily add Harry to the Geography lesson:
StudentToLesson::addMToMRelation($studentHarry, $lessonGeography);
//the above line created a StudentToLesson record with student_id = studentHarry's ID and lesson_id = lessonGeography's ID
//let's add Harry to another lesson
$lessonBiology = (new Lesson($persistence))->createEntity();
$lessonBiology->set('name', 'Biology');
$lessonBiology->save();
//adding/removing can either be done by passing the other model or only it's ID. In this case, we just pass the ID - that's what you typically get from UI
StudentToLesson::addMToMRelation($studentHarry, $lessonBiology->getId());
//this created another StudentToLesson record with student_id = studentHarry's ID and lesson_id = lessonBiology's ID
//Let's easily check if an MToM relation exists
StudentToLesson::hasMToMRelation($studentHarry, $lessonGeography); //true;
//harry is tired of Geography, lets remove him from this lesson:
StudentToLesson::removeMToMRelation($studentHarry, $lessonGeography);
//this removed the StudentToLesson Record linking Harry to Geography.
StudentToLesson::hasMToMRelation($studentHarry, $lessonGeography); //false
//Linda attends both courses. Let's add Linda to both courses. But this time we do it the other way around and pass the lesson model as first argument:
$studentLinda = (new Student($persistence))->createEntity();
$studentLinda->set('name', 'Linda');
$studentLinda->save();
StudentToLesson::addMToMRelation($lessonGeography, $studentLinda);
StudentToLesson::addMToMRelation($lessonBiology, $studentLinda);The sample code from this readme can be found in the docs directory.
The version numbers of this repository correspond with the atk4\data versions. So 4.0.x is compatible with atk4\data 4.0.x and so on.