How to ensure parameter contains a Collection or ArrayCollection in Symfony

I have 2 tables named "cred_pathway" and "course". They have a Many To Many relationship.

I defined the relationship in annotations as below.

/**
 * @var Course[]|ArrayCollection
 *
 * @ORM\ManyToMany(targetEntity="Course\Entity\Course", inversedBy="cred_pathway")
 * @ORM\JoinTable(name="cred_pathway_course",
 *   joinColumns={
 *     @ORM\JoinColumn(name="cred_pathway_id", referencedColumnName="id")
 *   },
 *   inverseJoinColumns={
 *     @ORM\JoinColumn(name="course_id", referencedColumnName="id")
 *   }
 * )
 */
private $credPathwayCourse;

I want to add a new course to the list if the course is not already available in the list.

 public function addCourse(Course $course) {
    if (!$this->credPathwayCourse->contains($course)) {
        $this->credPathwayCourse->add($course);
    }
}

But the problem is that $this->credPathwayCourse contains an array in runtime and it throws the below array because I am trying to access contains() function on an array.

Call to a member function contains() on array

Is there a way to make sure that $this->credPathwayCourse contains a Collection or an ArrayCollection?

You can typehint it like so:

private Collection $credPathwayCourse;

Then create a constructor to ensure that your property is set using the correct collection type:

public function __construct() {
    $this->credPathwayCourse = new ArrayCollection;
}

Note that an ArrayCollection implements the Collection interface, so if you decide that you want to use a different collection type down the road, you can just swap it out in your constructor.