Set Models
Table of Contents
Introduction
The set() operator is for setting a model in a DB. The input is a model, the model is written to the DB as a side effect, and the output is a list of errors if there are any errors.
set() operator
The set() operator is passed a model to be written to the DB, and a DB-specific delegate which does the actual writing to the DB. The operator returns a list of errors if any.
The set() operator first validates the model using SetRequestValidationVisitor. If there are errors, the operator aborts and returns the errors. Else the operator writes the model to the DB using SetDelegateVisitor and the delegate.
SetDelegateVisitor
The SetDelegateVisitor is initialized with the DB-specific delegate. When an entity is visited, it gathers the keys and non-composition fields from the entity, sorts the keys by their field numbers, and passes them to the delegate. Any errors returned by the delegate are accumulated in the visitor and returned by the set() operator at the end.
SetDelegate
This is an interface that DB-specific tree-ware libraries need to implement. The SetDelegateVisitor has to be initialized with an instance of an implementation. The implementation will be passed information necessary for saving an entity as a table row in the DB. The delegate returns any errors that it runs into while writing to the DB.