The most misunderstood part of magento is EAV, an advanced ORM.
EAV stands for Entity, Attribute and Value.
Databases were much simpler before magento.
While designing an ecommerce application one has a table containing lots of product information, another which contains category information and maybe another table that links the earlier two together.
Magento that two kinds of models a regular one and other is EAV.
Model Resource is something that makes the regular and EAV either.
Simple one inherits from Mage_Core_Model_Mysql4_Abstract, and EAV inherits from Mage_Eav_Model_Entity_Abstract.
This object attribute value model and open schema is a data model that can be used in case of number of attributes describing a thing which is very vast but actually apply to a given entity which is modest.
In EAV each entity is modelled and has various attributes.
Magento developers use EAV of generic ecommerce solution.
Not all open sources use EAV by default.
So magento developers have built an EAV system out of php objects using MySQL as a data store.
In magento development EAV is a nutshell.
Most of the people dealing with magento development would not need to do it but you need to understand the EAV resources for building it.
As the subject is very deep it is better to study up the MVC and its features first.
While creating a model with EAV resource we need to start setup and create module responding to following URL: example.
com/complexworld This resource has considered EAV.
Where does that file go? One of the trickiest part is to remember how classnames relate to file paths, and then ensure creating the correct named directory and class files.
After configuration it is useful to attempt to instantiate the class without creation of class files.
Additionally where new resource needs to be defined then it also serves as configuration check.
The model is independent and both the regular and EAV extends from same class.
EAV system knows which attributes a model uses while allows the linking of table storing values.
Systems and Applications: Magento is a system first and then an application.
So while building apps the system code is exposed in raw form.
While configuring EAV system in the same database you need to treat it as an old traditional machine.
Creating a setup resource: Specialized setup resource which is provided in magento which provides number of helper methods resulting into automatic creation of records.
Adding the entity type: By adding addEntityType method in the installer object which allows passing of entity type along with list of parameters by setting default values.
Creating the data tables: Addition of SQL tables helps in storing all the entity values and by configuring the system everything can be known about the tables.
Adding attributes: This would be the last step that needs taking setup resource which tells magento about what attributes that our model should have.
Further there are some things that are needed to do like configuring new entity, expecting the return value, arrays that defines attributes and tying all them together.
Attributes aren't limited to date, time, decimal, text and varchar.
EAV collections are tricky and especially when they are dealt with non-simple attributes.
There is no doubt that EAV Models are complicated part in Magento development.
You can offshore magento development from efficient and quality service providers.