CacheInterface In view cell

hello

I am trying to understand how view_cell work. I am reading view_cell doc guide and then check CI system. but I do not understand properly that how the interface can create an object?

File : System/view/cell.php

Code:

class Cell
{
    /**
     * Instance of the current Cache Instance
     *
     * @var CacheInterface
     */
    protected $cache;

    //--------------------------------------------------------------------

    public function __construct(CacheInterface $cache)
    {
        $this->cache = $cache;
    }

Can anyone explain in details how cell construct work?

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