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Virtual Objects
Once applications are written to make use of HALL objects, encounter situations where we want to make use of objects before they “exist”.
Example: Transactions and VTransactions
Simple pattern for building a virtual class:
- replace update() method with pass
- add a commit() method for converting to a real object
- add appropriate initialization information to the Factory class
- override methods so they work independent of data source.
Extremely useful in applications where we offer users “what if” scenarios