How to include and use custom class files in plugin?

I’m entirely new to OOP, but trying to dip my toe in by creating a simple Recipes plugin. I have added a Recipes custom post type and a few meta fields to go along with it, and now I am trying to create a few template files for displaying the recipe meta and content. To do this, I am thinking it would be useful to create a class to get all the meta for a particular post.

To test, I created a template file that is meant to echo one sentence with a single meta value after the post content:

$recipe = new Wp_Recipes_Recipe;
echo '<p>The prep time for this recipe is ' . $recipe->$recipeprep . '</p>';

And I created a new file in plugin-dir > public called “class-wp-recipes-recipe.php” that contains the following:

class Wp_Recipes_Recipe {

  public function __construct( $post_id ) {

    $this->$recipemeta = get_post_custom($post_id);
    $this->$recipeprep = $this->$recipemeta['_rcp-prep-time'][0];

  }

}

I think I need to add some code to specify to include my new file, but I am just not sure where to put it. I have tried putting a “require_once” for the file in the load_dependencies() function in the includes folder. No matter what I try, the meta value I am trying to display does not display, and the only noticeable effect from my efforts is that the wp admin bar no longer displays.

I may be going about this completely the wrong way, but any guidance would be greatly appreciated! Thanks!

Your constructor requires the post ID to be passed to the class when it’s instatiated, try this

$recipe = new Wp_Recipes_Recipe( get_the_ID() );