How to Create a Product Display Entity Reference and Block View of Related Products

This will guide you through creating a Related Products block for Drupal Commerce. I found this thread while looking for a solution myself. I am happy to answer any questions or suggestions for improvement.

Install the necessary modules

1. Download, Install, and Enable the "Entity Reference" module. http://drupal.org/project/entityreference

Creating the Reference Field

1. Create your product types and product display content types. For this example, the product display content types is labeled "Product Display".
2. Navigate to Structure -> Content Types -> Product Display -> Manage fields
3. Add a new Entity Reference field. For this example, the field is labeled "Related Products", and named "pd_related_products". The widget type is Autocomplete.
4. Choose the number of values. For this example, this is set to "Unlimited".
5. Select the "Target type" of "Node".
6. Select the target bundles. For this example, there is only one product display. Therefore, we highlight "Product Display".
7. Optionally, set the sort options. For this example, the field is sorted by the Title property in ascending order.

Configure the "Related Products" field in the dispaly

1. Navigate to Structure -> Content Types -> Product Display -> Manage display
2. For this example, the Related Products are shown in a block. Therefore, we hide this field from the display.

Add one or more Related Products to a Product Display

1. If it hasn't already been done, add a few sample products, and the accompanying product displays.
2. On at least one product display edit screen, choose the references to the product displays that will be listed as Related Products.

Create the View

1. Initial View Creation
   1. Navigate to Structure -> Add new view
   2. Choose a view name. In this example, the name is "Related Products".
   3. Choose Show: "Content", of type "Product Display", sorted by "Newest first".
   4. Uncheck the box reading "Create a page"
   5. Check the box reading "Create a block".
   6. Give the block a title, for this example the title is "Related Products".
   7. Select the desired number of items to display and pager settings.
   8. Click "Continue & edit".
2. Configure Filter Criteria
   1. In the "Filter criteria" heading, add a new filter of type "Global: PHP"
   2. In the "Filter code" section, add the following code:
      
        if (arg(0) && arg(0) == 'node') {
    $related_ids = array();
    $node = node_load(arg(1));
    $related = field_get_items('node',$node,'field_pd_related_products');
    if ($related && is_array($related) && sizeof($related) > 0) {
      for ($i=0; $i<=count($related); $i++ ) {
        $related_ids[] = $related[$i]['target_id'];
      }
    }
  }
  return ($related_ids && in_array($row->nid, $related_ids) ? FALSE : TRUE );
       
   3. Click on "Apply (all displays)"
3. Configure Relationship from the Product Display to its Products
   1. Expand the "Advanced" settings of the view configuration.
   2. In the "Relationships" heading, add a new relationship to "Content: Referenced product".
   3. Give this reference an identifier, for this example "Product Reference" was used.
   4. Apply this setting. Fields from the product entity will now be available as fields in the view.
4. Configure the Format
   1. In the "Format" heading, choose Format: "Unformatted list", Show: "Fields".
5. Configure the Fields
   1. In the "Fields" heading, add the following fields:
      • Content: Nid
        • Choose "Exclude from display" for this field. The Node ID is only needed for the filter settings above.
      • Content: Title
      • Commerce Product: Image
        • Choose Relationship: "Product".
        • Uncheck Create a label.
        • Formatter: "Image"
        • Image Style: [your desired image style]
        • Link image to: "Content"
      • Commerce Product: Price
        • Choose Relationship: "Product".
        • Formatter: Formatted amount
        • Choose "Display the calculated sell price for the current user.".
6. Configure Aggregation Settings
   1. In the "Advanced" heading, click on the link next to "Use aggregation".
   2. Check the "Aggregate" box.
7. Save the View

Configure the Block

1. Navigate to Structure -> Blocks.
2. Locate the "View: Related Products" block.
3. Choose the desired display region for this block. In this example, the region selected is "Second Sidebar" provided by the Zen theme.

Navigate to the Product Display that has Related Products to confirm everything worked.

Important Notes:

In the PHP code of the filter criteria, it is important that the field name matches the name of the field used as the entity reference. Also, the aggregation setting is required if there is more than one product referenced per product display node to avoid duplicate rows.