VoDbFieldInfo Function (DWord, DWord, Usual) |  |
Retrieve field definition information about a field.
Namespace: XSharp.RT
Assembly: XSharp.RT (in XSharp.RT.dll) Version: 2.19
SyntaxFUNCTION VoDbFieldInfo( kInfoType AS DWORD, wFieldPos AS DWORD, ptrRetVal REF USUAL ) AS LOGIC
Parameters
- kInfoType
- Type: DWord
Determines what type of information is retrieved. See the table in the Remarks section below. - wFieldPos
- Type: DWord
The position number of the field that you want information on. - ptrRetVal
- Type: Usual
A pointer to a polymorphic value.
This value will receive the requested information if the function is successful and will be unchanged otherwise.
If you just want to retrieve information, this value must be NIL before calling the function.
Although other RDDs may expand on this concept, the supplied RDDs limit using a non-NIL value to a single circumstance in which you can change the information rather than just retrieve it. With the DBS_ALIAS kInfoType, you can specify a non-NIL value, allowing you to specify a string that you can subsequently use to access the indicated field.
Return Value
Type: LogicTRUE if successful; otherwise, FALSE.
Remarks
VODBFieldInfo() is the same as DBFieldInfo(), except for the purpose of its third argument and the fact that it returns a logical.
This function, however, does not call the error handler and will not, therefore, produce a runtime error message or create an error object if it fails. Thus, it may be important to check the return value to determine if the function succeeded.
the LastRddError property in the runtime state. will contain needed information regarding any error that occurs.
See DbFieldInfo(Usual, Usual, Usual) for more information.
This function, however, does not call the error handler and will not, therefore, produce a runtime error message or create an error object if it fails. Thus, it may be important to check the return value to determine if the function succeeded.
the LastRddError property in the runtime state. will contain needed information regarding any error that occurs.
See DbFieldInfo(Usual, Usual, Usual) for more information.
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The values in the table below exist both as DEFINEs and also as members of the DbFieldInfo enum.
You can see the numeric values of the defines in the documentation of this Enum. |
| Constants | Description | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| DBS_NAME | Returns the name of the field. | ||||||||||||||||||
| DBS_TYPE | Returns the data type of the field. | ||||||||||||||||||
| DBS_LEN | Returns the length of the field. | ||||||||||||||||||
| DBS_DEC | Returns the number of decimal places for the field. | ||||||||||||||||||
| DBS_ALIAS | Returns and optionally changes an alternate name (or alias) by which a field can be referenced (by default, same as DBS_NAME). | ||||||||||||||||||
| DBS_PROPERTIES | Returns the number of properties defined for a field. | ||||||||||||||||||
| DBS_BLOB_DIRECT_LEN | Returns the length of data in a BLOB as an unsigned long integer, without referencing a particular memo field. For strings, the return value is the length of the string in bytes; for arrays, it is the number of elements in the first dimension; for all other data types, it returns -1. With this constant, you must specify the BLOB using a numeric pointer obtained from DBServer:BLOBDirectPut(), DBServer:BLOBDirectImport(), or DBServer:FieldInfo(DBS_BLOB_POINTER, ... />). | ||||||||||||||||||
| DBS_BLOB_DIRECT_TYPE |
To determine the data type of BLOB data, without reference to a particular memo field, use DBServer:FieldInfo(DBS_BLOB_DIRECT_TYPE, ...).
With this constant, you must specify the BLOB using a numeric pointer obtained from DBServer:BLOBDirectPut(), DBServer:BLOBDirectImport(),
or DBServer:FieldInfo(DBS_BLOB_POINTER, ...).
See DBS_BLOB_TYPE for a table of possible return values. | ||||||||||||||||||
| DBS_BLOB_LEN |
Returns the length of the BLOB data in a memo field as an unsigned long integer. For strings, the return value is the length of the string in bytes;
for arrays, it is the number of elements in the first dimension; for all other data types, it returns -1.
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| DBS_BLOB_POINTER | Returns a numeric pointer to the BLOB data associated with a memo field. | ||||||||||||||||||
| DBS_BLOB_TYPE |
Unlike memo fields maintained in .DBT files, BLOB files allow you to store many different types of data in memo fields.
However, the standard functions for determining data types, such as ValType(), simply treat BLOB fields as regular memo fields.
To determine the actual type of BLOB data stored in a memo field, use DBServer:FieldInfo(DBS_BLOB_TYPE, ...).
The data type of the return value is string and can be interpreted using this table:
| ||||||||||||||||||
| DBS_USER | Start of user defined DBS_ values. |
| Tip |
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| DBS_USER is a constant that returns the minimum value that third-party RDD developers can use for defining new properties. Values less than DBS_USER are reserved for X# development. |
Examples
The following examples use VODBFieldInfo() to retrieve field information:
X#
1FUNCTION ShowFieldInfo(wField AS WORD) AS VOID 2 LOCAL uResult AS USUAL 3 uResult := NIL 4 IF VODBFieldInfo(DBS_NAME, wField, @uResult) 5 ? "FieldName(): ", uResult 6 ELSE 7 DoError() 8 ENDIF 9 IF VODBFieldInfo(DBS_TYPE, wField, @uResult) 10 ? "Field type: ", uResult 11 ELSE 12 DoError() 13 ENDIF 14 IF VODBFieldInfo(DBS_LEN, wField, @uResult) 15 ? "Field length: ", uResult 16 ELSE 17 DoError() 18 ENDIF 19 IF VODBFieldInfo(DBS_DEC, wField, @uResult) 20 ? "Decimals: ", uResult 21 ELSE 22 DoError() 23 ENDIF 24 RETURN 25STATIC FUNCTION DoError() AS USUAL 26 LOCAL uRetCode AS USUAL 27 LOCAL oError AS USUAL 28 oError := ErrorBuild(RuntimeState.LastRddError) 29 oError:FuncSym := #VODBFieldInfo 30 RETURN EVAL(ErrorBlock(), oError)
See Also