TBufDataset class

In unit BufDataset

Implements a database-aware buffered dataset.

Declaration

pascal

TBufDataset = class(TCustomBufDataset)

Inheritance

Description

TBufDataset is a TCustomBufDataset descendant that implements a database-aware buffered dataset. TBufDataset is an in-memory dataset that can be used as a local stand-alone dataset, or it can be used as a local buffer for updates applied to a remote dataset. TBufDataset implements many features similar to those in TClientDataset in Delphi. However, it is not meant to be code or function compatible with TClientDataset. It is designed to provide management of the buffers used to access record data, and is used as the ancestor for classes like TSQLQuery and TRESTBufDataset.

As a TDBDataset descendent, it offers access to many of the database features supported in the FCL DB package. As a TDataset descendent, it also offers access to familiar navigation and data handling methods in the ancestor class. TBufDataset has features that allow local storage and retrieval of field definitions and record data. In addition, facilities are provided that allow local indexing of record data in the dataset. There is a comprehensive parser/expression evaluator available that allows complete support for Filters in the dataset.

TBufDataset sets the visibility for properties and methods defined in the ancestor class.

Additional information about using TBufDataset can be found on the Lazarus Wiki at: How to write in-memory database applications in Lazarus/FPC (TBufDataset).

Properties

`MaxIndexesCount`	published	Maximum number of indexes available in the dataset.
`FieldDefs`	published	Definitions of available fields in the underlying database.
`Active`	published	Is the dataset open or closed.
`AutoCalcFields`	published	How often should the value of calculated fields be calculated.
`Filter`	published	Filter to apply to the data in memory.
`Filtered`	published	Is the filter active or not.
`ReadOnly`	published	Indicates if records can be added, deleted, or modified in the dataset.
`AfterCancel`	published	Event triggered after a Cancel operation.
`AfterClose`	published	Event triggered after the dataset is closed.
`AfterDelete`	published	Event triggered after a successful Delete operation.
`AfterEdit`	published	Event triggered after the dataset is put in edit mode.
`AfterInsert`	published	Event triggered after the dataset is put in insert mode.
`AfterOpen`	published	Event triggered after the dataset is opened.
`AfterPost`	published	Event called after changes have been posted to the underlying database.
`AfterScroll`	published	Event triggered after the cursor has changed position.
`BeforeCancel`	published	Event triggered before a Cancel operation.
`BeforeClose`	published	Event triggered before the dataset is closed.
`BeforeDelete`	published	Event triggered before a Delete operation.
`BeforeEdit`	published	Event triggered before the dataset is put in edit mode.
`BeforeInsert`	published	Event triggered before the dataset is put in insert mode.
`BeforeOpen`	published	Event triggered before the dataset is opened.
`BeforePost`	published	Event called before changes are posted to the underlying database.
`BeforeScroll`	published	Event triggered before the cursor changes position.
`CancelChangesOnRefresh`	published

Methods

InternalRefresh protected Performs actions needed to refresh records in the dataset.

Events

`OnCalcFields`	published	Event triggered when values for calculated fields must be computed.
`OnDeleteError`	published	Event triggered when a delete operation fails.
`OnEditError`	published	Event triggered when an edit operation fails.
`OnFilterRecord`	published	Event triggered to filter records.
`OnNewRecord`	published	Event triggered when a new record is created.
`OnPostError`	published	Event triggered when a post operation fails.