TDataLink¶

Data event handling agent for controls.

Declaration¶

Source position: db.pas line 2011

type

  TDataLink = class(TPersistent)
  public
    constructor Create;
    destructor Destroy;
    function Edit : Boolean;
    procedure UpdateRecord;
    function ExecuteAction : Boolean;
    function UpdateAction : Boolean;
    property Active: Boolean; {r}
    property ActiveRecord: Integer; {rw}
    property BOF: Boolean; {r}
    property BufferCount: Integer; {rw}
    property DataSet: TDataSet; {r}
    property DataSource: TDataSource; {rw}
    property DataSourceFixed: Boolean; {rw}
    property Editing: Boolean; {r}
    property Eof: Boolean; {r}
    property ReadOnly: Boolean; {rw}
    property RecordCount: Integer; {r}
  end;

Inheritance¶

Description¶

TDataLink is used by GUI controls or datasets in a master-detail relationship to handle data events coming from a TDatasource instance. It is a class that exists for component programmers, application coders should never need to use TDataLink or one of it's descendents.

DB-Aware Component coders must use a TDatalink instance to handle all communication with a TDataset instance, rather than communicating directly with the dataset. TDataLink contains methods which are called by the various events triggered by the dataset. Inversely, it has some methods to trigger actions in the dataset.

TDatalink is an abstract class; it is never used directly. Instead, a descendent class is used which overrides the various methods that are called in response to the events triggered by the dataset. Examples are .

Properties¶

Member	Visibility	Description
Active read only	public	Is the link active.
ActiveRecord	public	Currently active record.
BOF read only	public	Is the dataset at the first record.
BufferCount	public	Set to the number of record buffers this datalink needs.
DataSet read only	public	Dataset this datalink is connected to.
DataSource	public	Datasource this datalink is connected to.
DataSourceFixed	public	Can the datasource be changed.
Editing read only	public	Is the dataset in edit mode.
Eof read only	public
ReadOnly	public	Is the link readonly.
RecordCount read only	public	Number of records in the buffer of the dataset.

See all Properties

Methods¶

Member	Visibility	Description
Create	public	Initialize a new instance of TDataLink.
Destroy	public	Remove an instance of TDatalink from memory.
Edit	public	Set the dataset in edit mode, if possible.
ExecuteAction	public	Execute action.
UpdateAction	public	Update handler for actions.
UpdateRecord	public	Called when the data in the dataset must be updated.

See all Methods

Name	Description
TDataset	Base class for records-based data-access.
TDatasource	Component representing the link between a local (GUI) component and a dataset.
TDetailDatalink	Represents the link between a detail data source and a master datasource.
TMasterDataLink	Datalink for Master-Detail relationships between datasets.