Modeling: User's Guide

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3. Functionalities for Object Management

All python objects must inherit from the framework class CustomObject, to be thus connected to the framework's core. The CustomObject class defines all the necessary logic to make it possible to ensure the objects' persistency within the RDBMS, as well as numerous functionalities to help you with your own business logic. For those purposes, it works with a model, from which the classes are generally generated.

This chapter presents some important issues that you should not forget when coding and customizing your classes and logic-particularly important are the methods willRead and willChange. We will also look at other functionalities you can take advantage of, among which: validation of the referential constraints and custom validation logic.

Note that, you may start working directly with the generated classes for your model-adding, modifying, and getting data (as explained in chapter 4)-and letting the framework do the above-mentioned tasks transparently. The information here is provided to allow you to better understand how the framework performs these tasks, and to thus make it easier to add to, or modify, the framework's default behaviour to better suit your application needs, e.g. to add custom validation logic.

Note: Only a small sampling of the methods and functionalities of the CustomObject class, and other supporting classes, are mentioned here. For a complete picture you will need to look at the source doc strings, for CustomObject itself, as well as the doc strings for the interfaces it implements, namely RelationshipManipulation, KeyValueCoding (these two interfaces are exposed in details in chapter 8) and DatabaseObject.

• 3.1 From model to python code
  • 3.1.1 Generating the python code
    • 3.1.1.1 The minimum
    • 3.1.1.2 Separating the generated code from your own work
  • 3.1.2 Building the python package dynamically, at run-time
    • 3.1.2.1 Dynamic generating of ``standard'' python code
    • 3.1.2.2 Dynamic generation using metaclass
  • 3.1.3 Static vs. dynamic: what's best?
• 3.2 The framework's requirements on python code
  • 3.2.1 Package's, modules' and classes' names
  • 3.2.2 Within classes
• 3.3 Automatic validation of referential and business-logic constraints
  • 3.3.1 Integrity constraints derived from the underlying model
  • 3.3.2 Checking constraints: key by key
    • 3.3.2.1 Return code
    • 3.3.2.2 How to define your own validation logic
  • 3.3.3 Validation.ValidationException: the list of error-codes
  • 3.3.4 Validating an object ``as a whole''
    • 3.3.4.1 validateForSave()
    • 3.3.4.2 validateForDelete()
  • 3.3.5 Misc.

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Modeling: User's Guide

Previous: 2.8 Some References on Up: 1 The essentials Next: 3.1 From model to

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Release 0.9, documentation updated on March 4, 2006.

Comments are welcome: Sebastien Bigaret / Modeling Home Page
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