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Release 3.0 Copyright ©1992 by NeXT Computer, Inc. All Rights Reserved. (Preliminary draft, Thurs Apr 16 16:12:34 PDT 1992) DBBasicAdaptorContext Inherits From: Object Declared In: dbkit/DBBasicAdaptor.h Class Description DBBasicAdaptorContext is the abstract superclass for objects that are used in adaptor context management. Basically, the context object provides a place to locate special accounting structures (such as cursors) used in the interpretation of query languages. The objects are used as though the adaptor delegates every call to evaluateString:using: and fetchData: to its context objects. Context objects are allocated as follows: adaptors have a single "shared context" which is used for the potentially destructive operations insert, update, evaluate, and delete. Contexts for select, on the other hand, are allocated on a per-binder basis, unless the binder has had its sharesContext flag set. If the binder returns YES to sharesContext, then all operations, including select, will use the adaptor's "shared context". Semantically, a select on a shared context should lock the selected data if possible -- a select on a shared context is normally followed quickly by an update. Of course, the context allocation scheme can be completely altered by reimplementing the DBBasicAdaptor -- it is not a requirement of the DBKit that it behave this way. Instance Variables None declared in this class. Method Types Creating a context - initForAdaptor: Evaluating expressions - evaluateString:using: - fetchData: Instance Methods initForAdaptor: - initForAdaptor:anAdaptor This method should prepare any data structures that the context will later need for execution. evaluateString:using: - (BOOL)evaluateString:(const unsigned char*)aString using:(DBBinder*)aBinder This method is called with a query expression as aString. The method should return its success in evaluating this expression. fetchData: - (BOOL)fetchData:(DBBinder*)aBinder This method is called after potentially data-producing operations. It should place the next available "row" of data into aBinder.
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