I've got a client database with a large range of stock items, which are being uploaded to Magento as simple products.
Now I need to group them up and assign them to configurable products with their size and colour being their configurable attributes.
The Magento API has a Product_Link class, with a promising looking method: catalogue-product-link.assign (link), but I can't for the life of me figure out what arguments I need to make it work with configurable products, providing this is how assign was meant to be used.
Best Answer
Well the notes here helped me get this running. So I thought I'd share with you the code to add a simple product to an existing Configurable Product.
This code assumes the simple product is a valid one to add, I'm not sure what would happen if it wasn't.