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Documentation > WebObjects 4.5 >
EOAccess Reference
(informal protocol)
Declared in: EOAccess/EOAdaptorChannel.h
Protocol Description
EOAdaptorChannel sends messages to its delegate for nearly
every operation that would affect data in the database server. The
delegate can use these methods to preempt these operations, modify
their results, or simply track activity.
Instance Methods
- (void)adaptorChannelDidChangeResultSet:(id)channel
Invoked from
fetchRowWithZone: when
a select operation resulted in multiple result sets. This method tells
the delegate that the next invocation of
fetchRowWithZone: will
fetch from the next result set. This method is invoked when
fetchRowWithZone: returns nil and
there
are still result sets left to fetch. The delegate can invoke
setAttributesToFetch: to
prepare for fetching the new rows.
- (void)adaptorChannel:(id)channel
didEvaluateExpression:(EOSQLExpression
*)expression
Invoked from
evaluateExpression: to
tell the delegate that a query language expression has been evaluated
by the database server.
- (void)adaptorChannel:(id)channel
didExecuteStoredProcedure:(EOStoredProcedure
*)procedure
withValues:(NSDictionary *)values
Invoked from
executeStoredProcedure:withValues: after
procedure is
executed successfully.
- (void)adaptorChannel:(id)channel
didFetchRow:(NSMutableDictionary
*)row
Invoked from
fetchRowWithZone: after
a row is fetched successfully. This method is not invoked if an exception
occurs during the fetch or if the same returns nil because there
are no more rows in the current result set. The delegate may modify
row,
which will be returned from
fetchRowWithZone:.
- (void)adaptorChannelDidFinishFetching:(id)channel
Invoked from
fetchRowWithZone: to
tell the delegate that fetching is finished for the current select operation.
This method is invoked when a fetch ends in
fetchRowWithZone: because
there are no more result sets.
- (NSException *)adaptorChannel:(id)channel
didPerformOperations:(NSArray
*)operations
exception:(NSException *)exception
Invoked from
performAdaptorOperations:.
exception is nil if
no exception was raised while
operations were
performed. Otherwise,
exception is
the raised exception. The delegate can return the same or a different
exception, which is re-raised by
performAdaptorOperations:,
or it can return nil to prevent the adaptor channel from raising
an exception.
- (void)adaptorChannel:(id)channel
didSelectAttributes:(NSArray *)attributes
fetchSpecification:(EOFetchSpecification
*)fetchSpecification
lock:(BOOL)flag
entity:(EOEntity *)entity
Invoked from
selectAttributes:fetchSpecification:lock:entity: to
tell the delegate that rows have been selected in the database server.
- (NSDictionary *)adaptorChannelShouldConstructStoredProcedureReturnValues:(id)channel
Invoked from
returnValuesForLastStoredProcedureInvocation to
tell the delegate that
channel is constructing
return values for the last stored procedure evaluated. If the delegate
returns a value other than nil, that value will be returned immediately
from
returnValuesForLastStoredProcedureInvocation.
- (BOOL)adaptorChannel:(id)channel
shouldEvaluateExpression:(EOSQLExpression
*)expression
Invoked from
evaluateExpression: to
tell the delegate that
channel is
sending an expression to the database server. The delegate returns YES to
permit the adaptor channel to send
expression to
the server. If the delegate returns NO, the adaptor channel does
not send the expression and returns immediately. When the delegate
returns NO, the adaptor channel expects that the implementor of
the delegate has done the work that
evaluateExpression: would
have done. The delegate can create a new EOSQLExpression and send
the expression itself before returning NO.
- (NSDictionary *)adaptorChannel:(id)channel
shouldExecuteStoredProcedure:(EOStoredProcedure
*)procedure
withValues:(NSDictionary *)values
Invoked from
executeStoredProcedure:withValues: to
tell the delegate that
channel is
executing a stored procedure. If the delegate returns a value other
than nil, that value is used as the arguments to the stored procedure
instead of
values.
- (NSDictionary *)adaptorChannel:(id)channel
shouldReturnValuesForStoredProcedure:(NSDictionary
*)returnValues
Invoked from
returnValuesForLastStoredProcedureInvocation to
tell the delegate that
channel is returning
values for a stored procedure. If the delegate returns a value other
than nil, that value is returned from
returnValuesForLastStoredProcedureInvocation instead
of
returnValues.
- (BOOL)adaptorChannel:(id)channel
shouldSelectAttributes:(NSArray
*)attributes
fetchSpecification:(EOFetchSpecification
*)fetchSpecification
lock:(BOOL)flag
entity:(EOEntity *)entity
Invoked from
selectAttributes:fetchSpecification:lock:entity: to
ask the delegate whether a select operation should be performed.
The delegate should not modify fetchSpecification. Instead, if the delegate
wants to perform a different select it should invoke
selectAttributes:fetchSpecification:lock:entity: itself
with a new fetch specification, and return NO (indicating that the
adaptor channel should not perform the select itself).
- (void)adaptorChannelWillFetchRow:(id)channel
Invoked from
fetchRowWithZone: to
tell the delegate that a single row will be fetched. The delegate
can determine the attributes used by the fetch by sending
attributesToFetch to
channel,
and can change the set of attributes to fetch by sending
setAttributesToFetch: to
channel.
The adaptor channel performs the actual fetch.
- (NSArray *)adaptorChannel:(id)channel
willPerformOperations:(NSArray
*)operations
Invoked from
performAdaptorOperations: to
tell the delegate that
channel is
performing the EOAdaptorOperations in
operations.
The delegate may return
operations or
a different NSArray for the adaptor channel to perform. If the delegate
returns nil, the adaptor channel does not perform the operations
and returns from the method immediately.
