Component for Delphi palette

TfrxIBXComponents is the first component we should create; it will be placed into FastReport component palette when registering engine (in the Delphi environment). As soon as this component is placed into a project, Delphi automatically adds link to our engine unit into “Uses” list. One should assign one more task in this component, i.e. to define DefaultDatabase property in it, which refers to existing connection to DB. By default, all TfrxIBXTable and TfrxIBXQuery components will refer to this connection. It is necessary to inherit component from TfrxDBComponents class:

  TfrxDBComponents = class(TComponent)
  public
    function GetDescription: String; virtual; abstract;
  end;

Description should be returned by one function only, for example ”IBX Components”. TfrxIBXComponents component implementation is as follows:

type
  TfrxIBXComponents = class(TfrxDBComponents)
  private
    FDefaultDatabase: TIBDatabase;
    FOldComponents: TfrxIBXComponents;
  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
    function GetDescription: String; override;
  published
    property DefaultDatabase: TIBDatabase read FDefaultDatabase write FDefaultDatabase;
  end;

var
  IBXComponents: TfrxIBXComponents;

constructor TfrxIBXComponents.Create(AOwner: TComponent);
begin
  inherited;
  FOldComponents := IBXComponents;
  IBXComponents := Self;
end;

destructor TfrxIBXComponents.Destroy;
begin
  if IBXComponents = Self then
    IBXComponents := FOldComponents;
  inherited;
end;

function TfrxIBXComponents.GetDescription: String;
begin
  Result := 'IBX';
end;

We define IBXComponents global variable, which will refer to TfrxIBXComponents component copy. If you place component into project several times (though it is senseless), you will nevertheless be able to save link to previous component and restore it after deleting component.

A link to connection to DB, which already exists in project, can be placed into DefaultDatabase property. The way we will write TfrxIBXTable, TfrxIBXQuery components allows them to use this connection by default (actually, this is what we need IBXComponents global variable for).