CFieldExchange Class
Supports the record field exchange (RFX) and bulk record field exchange (Bulk RFX) routines used by the database classes.
Syntax
class CFieldExchange
Members
Public Methods
Name | Description |
---|---|
CFieldExchange::IsFieldType | Returns nonzero if the current operation is appropriate for the type of field being updated. |
CFieldExchange::SetFieldType | Specifies the type of recordset data member — column or parameter — represented by all following calls to RFX functions until the next call to SetFieldType . |
Remarks
CFieldExchange
does not have a base class.
Use this class if you are writing data exchange routines for custom data types or when you are implementing bulk row fetching; otherwise, you will not directly use this class. RFX and Bulk RFX exchanges data between the field data members of your recordset object and the corresponding fields of the current record on the data source.
Note
If you are working with the Data Access Objects (DAO) classes rather than the Open Database Connectivity (ODBC) classes, use class CDaoFieldExchange instead. For more information, see the article Overview:Database Programming.
A CFieldExchange
object provides the context information needed for record field exchange or bulk record field exchange to take place. CFieldExchange
objects support a number of operations, including binding parameters and field data members and setting various flags on the fields of the current record. RFX and Bulk RFX operations are performed on recordset-class data members of types defined by the enum
FieldType in CFieldExchange
. Possible FieldType values are:
CFieldExchange::outputColumn
for field data members.CFieldExchange::inputParam
orCFieldExchange::param
for input parameter data members.CFieldExchange::outputParam
for output parameter data members.CFieldExchange::inoutParam
for input/output parameter data members.
Most of the class's member functions and data members are provided for writing your own custom RFX routines. You will use SetFieldType
frequently. For more information, see the articles Record Field Exchange (RFX) and Recordset (ODBC). For information about bulk row fetching, see the article Recordset: Fetching Records in Bulk (ODBC). For details about the RFX and Bulk RFX global functions, see Record Field Exchange Functions in the MFC Macros and Globals section of this reference.
Inheritance Hierarchy
CFieldExchange
Requirements
Header: afxdb.h
CFieldExchange::IsFieldType
If you write your own RFX function, call IsFieldType
at the beginning of your function to determine whether the current operation can be performed on a particular field or parameter data member type (a CFieldExchange::outputColumn
, CFieldExchange::inputParam
, CFieldExchange::param
, CFieldExchange::outputParam
, or CFieldExchange::inoutParam
).
BOOL IsFieldType(UINT* pnField);
Parameters
pnField
The sequential number of the field or parameter data member is returned in this parameter. This number corresponds to the data member's order in the CRecordset::DoFieldExchange or CRecordset::DoBulkFieldExchange function.
Return Value
Nonzero if the current operation can be performed on the current field or parameter type.
Remarks
Follow the model of the existing RFX functions.
CFieldExchange::SetFieldType
You need a call to SetFieldType
in your recordset class's DoFieldExchange or DoBulkFieldExchange override.
void SetFieldType(UINT nFieldType);
Parameters
nFieldType
A value of the enum FieldType
, declared in CFieldExchange
, which can be one of the following:
CFieldExchange::outputColumn
CFieldExchange::inputParam
CFieldExchange::param
CFieldExchange::outputParam
CFieldExchange::inoutParam
Remarks
For field data members, you must call SetFieldType
with a parameter of CFieldExchange::outputColumn
, followed by calls to the RFX or Bulk RFX functions. If you have not implemented bulk row fetching, then ClassWizard places this SetFieldType
call for you in the field map section of DoFieldExchange
.
If you parameterize your recordset class, you must call SetFieldType
again, outside any field map section, followed by RFX calls for all the parameter data members. Each type of parameter data member must have its own SetFieldType
call. The following table distinguishes the different values you can pass to SetFieldType
to represent the parameter data members of your class:
SetFieldType parameter value | Type of parameter data member |
---|---|
CFieldExchange::inputParam |
Input parameter. A value that is passed into the recordset's query or stored procedure. |
CFieldExchange::param |
same as CFieldExchange::inputParam . |
CFieldExchange::outputParam |
Output parameter. A return value of the recordset's stored procedure. |
CFieldExchange::inoutParam |
Input/output parameter. A value that is passed into and returned from the recordset's stored procedure. |
In general, each group of RFX function calls associated with field data members or parameter data members must be preceded by a call to SetFieldType
. The nFieldType parameter of each SetFieldType
call identifies the type of the data members represented by the RFX function calls that follow the SetFieldType
call.
For more information about handling output and input/output parameters, see the CRecordset
member function FlushResultSet. For more information about the RFX and Bulk RFX functions, see the topic Record Field Exchange Functions. For related information about bulk row fetching, see the article Recordset: Fetching Records in Bulk (ODBC).
Example
This example shows several calls to RFX functions with accompanying calls to SetFieldType
. Note that SetFieldType
is called through the pFX
pointer to a CFieldExchange
object.
void CSections::DoFieldExchange(CFieldExchange *pFX)
{
pFX->SetFieldType(CFieldExchange::outputColumn);
RFX_Text(pFX, _T("[CourseID]"), m_CourseID);
RFX_Text(pFX, _T("[InstructorID]"), m_InstructorID);
RFX_Text(pFX, _T("[RoomNo]"), m_RoomNo);
RFX_Text(pFX, _T("[Schedule]"), m_Schedule);
// output parameter
pFX->SetFieldType(CFieldExchange::outputParam);
RFX_Long(pFX, _T("Instructor_Count"), m_nCountParam);
// input parameter
pFX->SetFieldType(CFieldExchange::inputParam);
RFX_Text(pFX, _T("Department_Name"), m_strNameParam);
}
See also
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