TBufDataset¶

Implements a database-aware buffered dataset.

Declaration¶

Source position: bufdataset.pas line 696

type

  TBufDataset = class(TCustomBufDataset)
  published
    property MaxIndexesCount;
    property FieldDefs;
    property Active;
    property AutoCalcFields;
    property Filter;
    property Filtered;
    property ReadOnly;
    property AfterCancel;
    property AfterClose;
    property AfterDelete;
    property AfterEdit;
    property AfterInsert;
    property AfterOpen;
    property AfterPost;
    property AfterScroll;
    property BeforeCancel;
    property BeforeClose;
    property BeforeDelete;
    property BeforeEdit;
    property BeforeInsert;
    property BeforeOpen;
    property BeforePost;
    property BeforeScroll;
    property OnCalcFields;
    property OnDeleteError;
    property OnEditError;
    property OnFilterRecord;
    property OnNewRecord;
    property OnPostError;
    property CancelChangesOnRefresh: Boolean; {rwd}
  end;

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¶

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

See all Properties

Events¶

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

See all Events

Name	Description
TCustomBufDataset	Dataset connected to a database.
TDataset	Base class for records-based data-access.
TDBDataset	Dataset connected to a database.