DataServer Class |  |
Provide the base class from which all X# data servers are subclassed.
Inheritance HierarchyNamespace: VO
Assembly: VOSystemClasses (in VOSystemClasses.dll) Version: 2.21
SyntaxThe DataServer type exposes the following members.
Constructors| Name | Description | |
|---|---|---|
 | DataServer |
Construct a data server.
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Properties| Name | Description | |
|---|---|---|
 | BoF |
A logical value indicating whether this data server is positioned at the beginning of the file, on the first record (TRUE if yes, FALSE if no).
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| Clients | **Missing documentation ** |
| ConcurrencyControl |
A constant, identifying the mode of automatic concurrency control for this data server, determining when and how records are locked and released:
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| DBStruct |
An array containing the structure of this data server.
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| EoF |
A logical value indicating whether this data server is positioned at the end of the file, on the last record after an attempt to move beyond the last record (TRUE if yes, FALSE if no).
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| FCount |
The number of fields in this data server.
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| HLStatus | **Missing documentation ** |
 | HyperLabel |
The hyperlabel connected to this data server. From the hyperlabel, you can retrieve additional information about the data server
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| Name |
A string representing the name of this data server.
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| NameSym |
A symbol representing the name of this data server.
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| RecCount |
A numeric value representing the number of records in this data server.
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| RecNo |
A numeric value representing the current record number, identifying the position of the record pointer in this data server.
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| Status |
A hyperlabel identifying the status of this data server after the last operation.
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Methods| Name | Description | |
|---|---|---|
| Append |
Append a blank record to the end of this data server (the new record becomes the current position and is ready for assignment of data values).
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| AsString |
Return the descriptive label defined for this data server.
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| Close |
Close down the server in a manner specific to the database used.
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| Commit |
Force all pending updates to this data server to be permanently written to disk.
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| DataField |
Retrieve the DataField object at a specified field position.
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| Delete |
Delete the current record in this data server.
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| FIELDGET |
Return the contents of a specified field in this data server.
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| FieldGetFormatted |
Return the contents of a specified field in this data server, according to the formatting specifications of its FieldSpec.
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| FieldHyperLabel |
Return the hyperlabel defined for a field in this data server.
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| FieldName |
Return the name of a field in this data server.
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| FieldPos |
Return the position of a field in this data server.
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| FIELDPUT |
Assign a value to a field in this data server.
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| FieldSpec |
Return the FieldSpec object for a field in this data server.
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| FieldStatus |
Determine the status of a field in this data server after the last operation.
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| FieldSym |
Return the symbolic name of a field in this data server.
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| FieldValidate |
Perform all the validations defined to the FieldSpec of a field in this data server (for example, required, maximum and minimum digits, maximum and minimum value, validation rule) and return the result of the test.
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| FLOCK |
Lock this entire data server for exclusive access.
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| GoBottom |
Position this data server at the last record.
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| GoTo |
Position this data server on a specified record number.
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| GoTop |
Position this data server at the first record.
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| NoIVarGet |
Provide a general error interception that is automatically called (in any class) whenever an access reference is made to a non-existent exported instance variable. In the DataServer class, it is used to implement the virtual field variable.
Important! NoIVarGet() should not be called directly; it is called by the system for handling invalid references. |
| NoIVarPut |
Provide a general error interception that is automatically called (in any class) whenever an assignment reference is made to a non-existent exported instance variable. In the DataServer class, it is used to implement the virtual field variable.
Important! NoIVarPut() should not be called directly; it is called by the system for handling invalid references. |
| Notify |
An event handler that responds to events that have occurred in methods of this server, or in other servers that are linked to this server in some way. The standard implementation notifies all the server's clients of the event.
Description
Important! This method is automatically called by the various action methods of the data server, and should normally not be called by application code. |
| PostInit |
Implement customized initialization code for the window.
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| PreInit |
Implement customized initialization code for the server.
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| RegisterClient |
Register an object as a client of this data server, so that it receives notification messages from the server about certain actions.
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| ResetNotification |
Resume the broadcasting of Notify messages to the server's attached clients (after DataServer:SuspendNotification() has been called).
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| RLOCK |
Lock a specific record in this data server for exclusive write access; other users can still make read-only reference to the record.
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| RLockVerify |
Determine if the current record in this data server has any pending updates and lock it for exclusive write access if there are none.
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| Rollback |
Undo the changes made to this data server within the current transaction.
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| Seek |
Move to the next record having a specified key value in the controlling order.
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| SetDataField |
Assign a DataField object to a specified field in this data server.
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| Skip |
Move the record pointer forward or backward in this data server a specified number of records.
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| SuspendNotification |
Suspend the broadcasting of Notify messages to the server's attached clients.
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| UnLock |
Remove all locks held on this data server.
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| UnRegisterClient |
Remove the registration of an object as a client of this data server, so that it no longer receives notification messages from the server about certain actions.
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| Update |
Update this server with data from another server or table.
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RemarksImportant! DataServer is an abstract class and should not be used directly — instead, use one of its subclasses, which include DBServer and SQLSelect. The documentation in this class is provided for the purposes of creating a DataServer subclass and details the data server entities that should be implemented for a consistent interface to other X# components (for example, a data window). This abstract class defines the common protocol — properties and behavior — used by the various X# data servers. These data servers provide an object-oriented interface to databases in many contexts, but they are particularly useful as drivers for the DataWindow class. For example, any class that derives from DataServer can be connected as a server to a data window or data browser.
See Also