Data Cursor

TDataCursor

Any TDataItem can be sorted and filtered without altering its data arrays. TDataCursor creates a "view" of a data table or column. A "view" is essentially an index (an array of row integer positions).

TBIDataSet component includes a TDataCursor property to perform these operations, which in turn are used in TBIGrid and TBIChart.

A TDataCursor can also be used when exporting data (to JSON, XML, CSV, Excel, TDataSet, HTML, etc).

The TDataCursor "Loop" method sorts and filters data and traverses the resulting view, calling a user-defined procedure:

uses BI.DataSource, BI.Arrays;
var MyCursor : TDataCursor;
MyCursor:= TDataCursor.Create;
MyCursor.Data:= Orders;

// .... we can set here the SortBy, Filter, etc properties...

MyCursor.Loop( procedure( const AIndex: TInteger)
    begin
      WriteLn( Orders['ProductID'].DataToString( AIndex ) );
    end);

This is equivalent to calculating the cursor "Index" and doing a "for" loop on the index:

var t : Integer;
MyCursor.PrepareIndex;
for t:=0 to High(MyCursor.Index) do
    WriteLn( Orders['ProductID'].DataToString( MyCursor.Index[t] ) );