TFieldDataLink class

In unit DBCtrls

Maintains an association between a control, an action, and a field in a linked dataset.

Declaration

pascal

TFieldDataLink = class(TDataLink)

Inheritance

TFieldDataLink
TDataLink
TPersistent
TObject

Description

TFieldDataLink is a TDataLink descendant which maintains an association between a control, an action, and a field in a linked dataset. TFieldDataLink extends the ancestor class to provide additional properties, methods, and events useful when working with a data-aware control linked to a field in a dataset.

The following key properties are added in the class:

Control
FieldName
Field

The following events are added in the class:

OnDataChange
OnUpdateData
OnEditingDone
OnActiveChange

TFieldDataLink is used in the implementation of several data-aware controls. In most cases, it is used in an internal member and not exposed in the interface for the control. It can, however, be used as a public or published property.

Properties

`Control`	public	The Control to which this datalink is attached.
`Field`	public	The Field to which the datalink is attached.
`FieldName`	public	FieldName - the name of the attached field, stored as a string.
`CanModify`	public	True if the linked field is capable of being modified.
`Editing`	public	True if the linked field is being edited.
`EditingSource`	public	Indicates if the data link is changing its source properties.

Methods

`ActiveChanged`	protected	ActiveChanged - method to process changes in the Active property.
`EditingChanged`	protected	EditingChanged - method for processing changes in the Editing property.
`LayoutChanged`	protected	LayoutChanged- called if layout is changed: tests validity of field then calls OnLayoutChange event handler.
`RecordChanged`	protected	RecordChanged - triggered if the contents of the current record change; calls Reset.
`UpdateData`	protected	Signals the OnUpdateData event handler for pending changes to the linked dataset.
`FocusControl`	protected	FocusControl gives the input focus to the data-aware control in the class instance.
`Create`	public	Constructor for the class instance.
`Edit`	public	Edit - if the field can be modified, performs inherited Edit and shows editing status.
`Modified`	public	Updates the class when the linked dataset enters an edit state.
`Reset`	public	Checks whether the link is active, calls the OnDataChange event handler then sets IsModified to False.

Events

`OnDataChange`	public	Event handler signalled when the field data link has been changed.
`OnEditingChange`	public	OnEditingChange - event handler for a changed in the Editing property.
`OnUpdateData`	public	OnUpdateData - event handler for updating any pending changes in the data.
`OnActiveChange`	public	OnActiveChange - event handler for a change in the Active property.

Inherited

From TDataLink (28)

Active ActiveRecord BOF BufferCount CheckBrowseMode DataEvent DataSet DataSetChanged DataSetScrolled DataSource DataSourceFixed Destroy Eof ExecuteAction FirstRecord GetActiveRecord GetBOF GetBufferCount GetEOF GetRecordCount MoveBy ReadOnly RecordCount SetActiveRecord SetBufferCount UpdateAction UpdateRecord VisualControl

From TPersistent (8)

Assign AssignTo DefineProperties FPOAttachObserver FPODetachObserver FPONotifyObservers GetNamePath GetOwner

From TObject (40)

AfterConstruction BeforeDestruction CheckDisposed ClassInfo ClassName ClassNameIs ClassParent ClassType CleanupInstance DefaultHandler DefaultHandlerStr Dispatch DispatchStr Disposed DisposeOf Equals FieldAddress Free FreeInstance GetDisposed GetHashCode GetInterface GetInterfaceByStr GetInterfaceEntry GetInterfaceEntryByStr GetInterfaceTable GetInterfaceWeak GetLastCastErrorInfo InheritsFrom InitInstance InstanceSize MethodAddress MethodName newinstance QualifiedClassName SafeCallException StringMessageTable SystemHasExtendedRTTI ToString UnitName

An experiment, built from development snapshots. Not the official Free Pascal or Lazarus documentation.