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Annotation of Examples/DatabaseKit/Evaluator/MultiBinder.h, revision 1.1.1.1

1.1       root        1: 
                      2: /*
                      3: MultiBinder.h
                      4: A Binder that knows about multiple result sets 
                      5: 
                      6: MultiBinders are used instead of DBBinders in order to retrieve
                      7: non-rectangular return results from Sybase or other similar stored
                      8: procedures.
                      9: 
                     10: MultiBinders only work in the mode where the binder itself creates
                     11: the recordPrototype for the binder.  You cannot provide your own
                     12: recordPrototypes for the MultiBinder.
                     13: 
                     14: If you know exactly the sequence of properties the stored procedure
                     15: will be returning to you, then:
                     16: 1.  Create a List for each [rectangular] result set the stored
                     17:     procedure returns.  Each List should contain, in the order the
                     18:     stored procedure will return them, the attributes returned from
                     19:     the database model.  Note that the attributes need not, in
                     20:     the case of the MultiBinder, be from the same entity.
                     21: 2.  Place all these Lists, in the order in which those result
                     22:     sets will be returned by the stored procedure, into a temporary
                     23:     List.  Pass that temporary list as the argument to
                     24:     [multiBinder initFromPropertyLists:].  After initializing the binder,
                     25:     the temporary list may be freed.  The underlying lists created in
                     26:     step #1 are now owned by the MultiBinder, and will be freed
                     27:     when the MultiBinder is freed.
                     28: 3.  Invoke the stored procedure via [multiBinder evaluateString:].
                     29: 4.  Repeatedley call [multiBinder setNext].  You can then call 
                     30:     [multiBinder valueForProperty:] for each property.  Use the 
                     31:     delegate method binderDidChangeResultSet: to find out when you
                     32:     cross result set boundaries.
                     33: 5.  All result sets have been retrieved when [multiBinder setNext]
                     34:     returns nil.  Note that you should have received as many calls
                     35:     to binderDidChangeResultSet: as there were result sets returned
                     36:     from your stored procedure.
                     37: 
                     38: If you want to simply receive whatever the stored procedure happens
                     39: to return, either because of your programs' task or because the 
                     40: stored procedure conditionally returns different things:
                     41: 1.  Pass nil as the argument to [MultiBinder initFromPropertyLists:].
                     42: 2.  Repeatedley call [multiBinder setNext].  You should interrogate
                     43:     the binder via [multiBinder getCurrentProperies:] to get the
                     44:     new list of properties whenever the delegate method
                     45:     binderDidChangeResultSet: is called.  DO NOT call getProperties:.
                     46: 3.  All rows of all result sets are retrieved when 
                     47:     [multiBinder setNext] returns nil.
                     48: 
                     49: */
                     50: 
                     51: #import <dbkit/dbkit.h>
                     52: 
                     53: @interface MultiBinder:DBBinder
                     54: {
                     55:     unsigned int       currentResultSet; /*  index into the list of lists */
                     56:     List               *propListList; /* a list of property lists for the result sets */
                     57: }
                     58: 
                     59: - initFromPropertyLists:(List *)propLists; /*  copies subsidiary lists out of propLists */
                     60: - (unsigned int)currentResultSet; /* returns the index of the current result set */
                     61: - (List *)getCurrentProperties:(List *)aList; /* fills aList with the current properties */
                     62: 
                     63: @end
                     64: 
                     65: @interface Object (MultiBinderDelegateMethods)
                     66: - binderWillChangeResultSet:binder; /* called before changing result sets */
                     67: - binderDidChangeResultSet:binder; /* called before fetching from a new result set */
                     68: @end
                     69: 
                     70: @interface DBBinder (MultiBinderMethods)
                     71: - (List *)getCurrentProperties:(List *)aList;
                     72: @end
                     73: 

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