Retrieving additional data from already loaded Magento models

Question

There are some occasions where I'm handed a model containing only some of the data I require, for example a catalog/product instances that doesn't contain certain attributes I may need to use, such as size, widget number, or waist measurement.

To alleviate this, my current options are:

• Create a new block, and load the required attributes manually using addAttributeToSelect($name).
• Loading the entire model in the template using the ID from the current, inadequately populated, model with, for example, Mage::getModel('catalog/product')->getId($product->getId()).

To my question: is there a way I can pick additional attributes that I'd like to load in my model collection after ->load() has been called? Also, is there a method to do this on individual models?

Answer 1

The right and most safe approach (but not the best - see below) is described in question - it is to load product once again.

There are no already developed methods to add more attributes, after the product is loaded, for several reasons:

1) During Model lifetime a lot its values are calculated and cached inside the Model. Thereby adding more attributes (e.g. price) will change the Model's state, but won't affect results of several methods, that are designed to return these attributes values (e.g. getPrice()), but internally do some additional preprocessing and depend on previously calculated data.

2) The Model's state will be inconsistent, as some methods will return cached and currently non-valid values, calculated on previous empty attribute, while some other methods will return non-cached values. So usage of such Model will be unsafe and its properties will be unpredictable.

3) Complexity of code to support such reloading is quite big.

Solutions

1) The first good solution (although is the heaviest one) is to load product once again, every time your block/model/helper needs extended set of attributes in it.

2) Better solution - is to load new collection with all products having all additional attributes, whenever you see, that these attributes will be required and original collection doesn't have them.

3) The best solution - is to load original product collection with all required attributes. Sometimes collections really load products with subset of possible attributes - mainly it is a legacy code for EAV optimization (now flat tables are turned 'on' by default and this optimization is not needed) or possibly when collection is loaded by search engine (e.g. Solr in Magento EE) which, by default, doesn't store all the attributes in its records.

3.1) You can add required attributes to the original collection at the place, where it is instantiated - via mentioned in question addAttributeToSelect($attributeNames) method

3.2) You can add your attributes to the list of attributes, automatically populated in a collection. Attributes lists differ from module to module, and they are stored in different places. Some are in config, others - in database. Concrete place (config or db table), where to add attributes for auto-population, depends on your concrete case.

4) Sometimes, when you need only attribute values, it maybe much easier and faster to write Resource Model, that will directly load them from DB by productIds and current storeId scope. Then you can take risk an set them as properties to Products in a collection or safely set them to Products as myAdditionalAttribuesValuesArray property or use as independent array, mapped to product ids.