Most applications do not explicitly create instances of TBooleanField. Instead, the field components are created automatically, as persistent field components defined in the Fields editor at design time or as dynamic field components created automatically by the dataset. 

Create sets the DataType property to ftBoolean and initializes the strings associated with Boolean values to 'True' and 'False'. The AOwner parameter specifies the component, typically a dataset, that becomes the new field's Owner. The Owner is responsible for freeing the component. 

In the rare cases when you must create a persistent field component at runtime, call Create to create and initialize an instance of TBooleanField. After instantiating a TBooleanField, associate it with a specific field by setting its FieldName property to the name of the field. Give the TBooleanField a unique identifier in the Name property. Establish where the field appears in the collection of fields by providing an ordinal number in the Index property. Associate the TBooleanField with a dataset component by setting its DataSet property to the name of the dataset component. 

The example below creates a TBooleanField object for a field named PaidInFull accessed through a TClientDataSet named ClientDataSet1.

var
  T: TBooleanField;
begin
  ClientDataSet1.Close;
  T := TBooleanField.Create(ClientDataSet1);
  T.FieldName := 'PaidInFull';
  T.Name := ClientDataSet1.Name + T.FieldName;
  T.Index := ClientDataSet1.FieldCount;
  T.DataSet := ClientDataSet1;
  ClientDataSet1.FieldDefs.UpDate;
  ClientDataSet1.Open;
end;

ClientDataSet1->Close();
TBooleanField *T = new TBooleanField(ClientDataSet1);
T->FieldName = "PaidInFull";
T->Name = ClientDataSet1->Name + T->FieldName;
T->Index = ClientDataSet1->FieldCount;
T->DataSet = ClientDataSet1;
ClientDataSet1->FieldDefs->UpDate();
ClientDataSet1->Open();

Destroy 

Create 

DataType