How should one structure validation, preparation and arrangement (etc) of data before dealing with the DB?
The data I expect to be passed might need to be validated (ex: category books actually exists) or contain conditional values (ex: sale price should only be set if ad = sale) or values that must be converted to ids (ex: category books must be converted to category_id 123).
I imagine that there are numerous ways to go about this like clumping everything together, grouping by field (do validation, prep etc together per field) or separating by action (validation, prep, etc) and field.
Are there any concepts when it comes to this topic just like the concept of MVC exists? Achieving flexibility, ease of maintenance or something like that?
Anything relating to common used components of model?
(I’m not sure if it helps but I’m currently using CodeIgniter / PHP)
In codeigniter, you can use the Form_Validation class with a callback method that you create. http://codeigniter.com/user_guide/libraries/form_validation.html#callbacks.
In your callback method you can check to see if things exist in database, etc.