TComponent.Components Property

Lists all components owned by the component.

Pascal

property Components [Index: Integer]: TComponent;

C++

__property TComponent * Components[int Index];

Description

Use Components to access any of the components owned by this component, such as the components owned by a form. The Components property is most useful when referring to owned components by number rather than name. It is also used internally for iterative processing of all owned components.

Index ranges from 0 to ComponentIndex minus 1.

C++ Examples:

Copy Code

/*
This code fragment moves any nonvisual components on the 
form into a separate data module. Note that the components 
are removed starting with the last component, so that the 
unprocessed portion of the Components array does not change.
Note: This code does not save the form or data module to disk
after the nonvisual components are moved.  If executed at 
runtime, the effect will not persist.
Add a second TForm and name it ComponentCount2.  Put 
"#include ComponentCount2.cpp" in ComponentCount.h.  
Place a TMemo in each form and a TButton in Form1.
*/

void __fastcall TForm1::Button1Click(TObject *Sender)
{
  int I;
  TComponent *Temp;
  Memo1->Lines->Add("Components removed: ");
  Form2->Memo1->Lines->Add("Components added: ");
  for (I = ComponentCount - 1; I >= 0; I--)
  {
    Temp = Components[I];
    // only move components that are not controls
    if (dynamic_cast<TControl *>(Temp) == NULL)
    {
      RemoveComponent(Temp);
      Memo1->Lines->Add(Temp->Name);
      Form2->InsertComponent(Temp);
      Form2->Memo1->Lines->Add(Temp->Name);
    }
  }
}

Copy Code

/*
This example fills a list box with the names of TDataSources
that are present and then fills a DBGrid a second form with
the data from the selected data source.  The DBGrid is not
filled in until Form2 is activated.  Here is the code for Form1
that fills the list box.
*/

TForm1 *Form1;
TTable *Customers, *Blobs;
Boolean Form1Done = False;

void CreateCustSource()
{
  Customers = new TTable(Form1); // The owner will clean this up.
  Customers->Active = false; // The Table component must not be active
  Customers->DatabaseName = "DBDEMOS";
  Customers->TableType = ttParadox;
  Customers->TableName = "CustInfo";
  Customers->Active = False;
  if (Customers->Exists) // Don't overwrite an existing table
  {
    Customers->Close();
    Customers->DeleteTable();
  }
  // The Table component must not be active
  // First, describe the type of table and give
  // it a name
  // Next, describe the fields in the table
  Customers->FieldDefs->Clear();
  TFieldDef *pNewDef = Customers->FieldDefs->AddFieldDef();
  pNewDef->Name = "Field1";
  pNewDef->DataType = ftInteger;
  pNewDef->Required = true;
  pNewDef = Customers->FieldDefs->AddFieldDef();
  pNewDef->Name = "Field2";
  pNewDef->DataType = ftString;
  pNewDef->Size = 30;
  // Next, describe any indexes
  Customers->IndexDefs->Clear();
  /* the 1st index has no name because it is a Paradox primary key */
  Customers->IndexDefs->Add("","Field1", TIndexOptions() <<ixPrimary << ixUnique);
  Customers->IndexDefs->Add("Fld2Index","Field2", TIndexOptions() << ixCaseInsensitive);
  // Now that we have specified what we want, create the table
  Customers->CreateTable();
  Customers->Active = True;
  for (int i = 1; i <= 20; i++)
    Customers->AppendRecord(ARRAYOFCONST((i*111, i*222)));
  Form1->CustomerDS->DataSet = Customers;
  Customers->Active = True;
}

void CreateBlobSource()
{
  int i;
  Blobs = new TTable(Form1);
  Blobs->DatabaseName = "DBDEMOS";
  Blobs->TableType = ttParadox;
  Blobs->TableName = "MyBlobInfo";
  Blobs->Active = False;
    // Don't overwrite an existing table
//    if Blobs.Exists then
//      MessageDlg('CustInfo table already exists.', mtWarning, [mbOK], 0)
//    else
  if (Blobs->Exists)
  {
    Blobs->Close();
    Blobs->DeleteTable();
  };
  // The Table component must not be active }
  // First, describe the type of table and give }
  // it a name }
  // Next, describe the fields in the table }
  Blobs->FieldDefs->Clear();
  TFieldDef *newDef = Blobs->FieldDefs->AddFieldDef();
  newDef->Name = "Field1";
  newDef->DataType = ftInteger;
  newDef->Required = True;
  newDef = Blobs->FieldDefs->AddFieldDef();
  newDef->Name = "Field2";
  newDef->DataType = ftBlob;
  newDef->Size = 30;
  // Next, describe any indexes }
  Blobs->IndexDefs->Clear();
  // The 1st index has no name because it is
  // a Paradox primary key }
  TIndexDef *newIDef = Blobs->IndexDefs->AddIndexDef();
  newIDef->Name = "";
  newIDef->Fields = "Field1";
  newIDef->Options << ixPrimary;
/*
        with AddIndexDef do
        begin
          Name := 'Fld2Indx';
          Fields := 'Field2';
          Options := [ixCaseInsensitive];
        end;
*/
  // Call the CreateTable method to create the table }
  Blobs->CreateTable();
  Blobs->Active = True;
  for (int i = 1; i <= 20; i++)
    Blobs->AppendRecord(ARRAYOFCONST((i*111, IntToStr(i*222))));
  Form1->BlobDS->DataSet = Blobs;
  Blobs->Active = True;
};


void __fastcall TForm1::FormCreate(TObject *Sender)
{
  CreateCustSource();
  CreateBlobSource();
  for (int i = 0; i < ComponentCount; i++)
  {
    if (Components[i]->ClassNameIs("TDataSource"))
      ListBox1->Items->AddObject(Components[i]->Name,
         dynamic_cast<TObject *>(Components[i]));
  }
}

void __fastcall TForm1::ListBox1MouseDown(TObject *Sender, TMouseButton Button, TShiftState Shift,
          int X, int Y)
{
  Form1Done = True;
}

Copy Code

/*
The following code sets the DataSource for a DBGrid
component in Form2 to the currently selected data source in
a list provided in Form1. This allows users to specify the
desired information in Form1, and then move to Form2 to view
the information. Select an item in the listbox and then
activate Form2 by clicking in it. Also, set the visible property
of Form2 to true.
*/
void __fastcall TForm2::FormActivate(TObject *Sender)
{
  if (Form1Done)
  {
    DBGrid2->DataSource =
      dynamic_cast<TDataSource *>(Form1->ListBox1->Items->Objects[Form1->ListBox1->ItemIndex]);
    DBNavigator2->DataSource =
      dynamic_cast<TDataSource *>(Form1->ListBox1->Items->Objects[Form1->ListBox1->ItemIndex]);
  };
}

Delphi Examples:

Copy Code

{
This code fragment moves any nonvisual components on the 
form into a separate data module. Note that the components 
are removed starting with the last component, so that the 
unprocessed portion of the Components array does not change.
Note: This code does not save the form or data module to disk
after the nonvisual components are moved.  If executed at 
runtime, the effect will not persist.
Add a second TForm and name it ComponentCount2.  Put 
"ComponentCount2" at the end of the uses clause of Form1.  
Place a TMemo in each form and a TButton in Form1.
} 

procedure TForm1.Button1Click(Sender: TObject);
var
  I: Integer;
  Temp: TComponent;
begin
  Form1.Memo1.Lines.Add('Components removed: ');
  Form2.Memo1.Lines.Add('Components added: ');
  for I := ComponentCount - 1 downto 0 do
  begin
    Temp := Components[I];
    if not (Temp is TControl) then
    begin
      RemoveComponent(Temp);
      Form1.Memo1.Lines.Add(Temp.Name);
      Form2.InsertComponent(Temp);
      Form2.Memo1.Lines.Add(Temp.Name);
    end;
  end;
end;

Copy Code

{
This example fills a list box with the names of TDataSources
that are present and then fills a DBGrid a second form with 
the data from the selected data source.  The DBGrid is not 
filled in until Form2 is activated.  Here is the code for Form1
that fills the list box.
}
var
  Form1: TForm1;
  Customers: TTable;
  Blobs: TTable;
  Form1Done : Boolean;
  procedure CreateMyTable;
  procedure CreateCustSource;
  procedure CreateBlobSource;

implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
var
  I: Integer;
begin
  CreateCustSource;
  CreateBlobSource;
  for I := 0 to ComponentCount - 1 do
  begin
    if (Components[I] is TDataSource) then
      ListBox1.Items.AddObject(Components[I].Name,
        Components[I] as TObject);
  end;
end;

procedure CreateCustSource();
begin
  Customers:= TTable.Create(Form1);
  with Customers do
  begin
    DatabaseName := 'DBDEMOS';
    TableType := ttParadox;
    TableName := 'MyCustInfo';
    ReadOnly:= False;

//    Don't overwrite an existing table
//    Looking for c:/ProgramFiles/Common Files/Codegear Shared/Data/dbdemos.gdb
    if (not Customers.Exists) then CreateMyTable
    else
    begin
      if (Customers.Exists AND
        (MessageDlg('MyCustInfo table already exists.  Do you want to rebuild it?', mtConfirmation, [mbYes, mbNo], 0) = mrYes)) then
      begin
        Customers.Close;
        Customers.DeleteTable;
        CreateMyTable;
      end;
    end;
  end;
  Form1.CustomerDS.DataSet:= Customers;
  Customers.Active:= True;
end;

procedure CreateMyTable();
var
  i: Integer;
begin
//      The Table component must not be active
//      First, describe the type of table and give
//      it a name
//      Next, describe the fields in the table
  with Customers do
  begin
      with FieldDefs do
      begin
        Clear;
        with AddFieldDef do
        begin
          Name := 'Field1';
          DataType := ftInteger;
          Required := True;
        end;
        with AddFieldDef do
        begin
          Name := 'Field2';
          DataType := ftString;
          Size := 30;
        end;
        with AddFieldDef do
        begin
          Name := 'Field3';
          DataType := ftString;
          Size := 30;
        end;
        with AddFieldDef do
        begin
          Name := 'Field4';
          DataType := ftString;
          Size := 30;
        end;
      end;

//    Take out this part to remove indexing
//    Next, describe any indexes
      with IndexDefs do
      begin
        Clear;
//        The 1st index has no name because it is
//        a Paradox primary key
        with AddIndexDef do
        begin
          Name := '';
          Fields := 'Field1';
          Options := [ixPrimary];
        end;
        with AddIndexDef do
        begin
          Name := 'Fld2Indx';
          Fields := 'Field2';
          Options := [ixCaseInsensitive];
        end;
      end;

//      Call the CreateTable method to create the table
      CreateTable;
      Customers.Active:= True;
      for i := 1 to 20 do
        Customers.AppendRecord([i*111, i*222, i*333, i*444]);
    end;
end;

procedure CreateBlobSource;
var
  i: Integer;
begin
  Blobs:= TTable.Create(Form1);
  with Blobs do
  begin
    DatabaseName := 'DBDEMOS';
    TableType := ttParadox;
    TableName := 'MyBlobInfo';
    Blobs.Active := False;
    { Don't overwrite an existing table }
//    if Blobs.Exists then
//      MessageDlg('CustInfo table already exists.', mtWarning, [mbOK], 0)
//    else
    begin
      if (Blobs.Exists) then
      begin
        Blobs.Close;
        Blobs.DeleteTable;
      end;
      { The Table component must not be active }
      { First, describe the type of table and give }
      { it a name }
      { Next, describe the fields in the table }
      with FieldDefs do
      begin
        Clear;
        with AddFieldDef do
        begin
          Name := 'Field1';
          DataType := ftInteger;
          Required := True;
        end;
        with AddFieldDef do
        begin
          Name := 'Field2';
          DataType := ftBlob;
          Size := 30;
        end;
      end;
      { Next, describe any indexes }
      with IndexDefs do
      begin
        Clear;
        { The 1st index has no name because it is
        { a Paradox primary key }
        with AddIndexDef do
        begin
          Name := '';
          Fields := 'Field1';
          Options := [ixPrimary];
        end;
{
        with AddIndexDef do
        begin
          Name := 'Fld2Indx';
          Fields := 'Field2';
          Options := [ixCaseInsensitive];
        end;
}
      end;
      { Call the CreateTable method to create the table }
      CreateTable;
      Blobs.Active:= True;
      for i := 1 to 20 do
        Blobs.AppendRecord([i*111, IntToStr(i*222)]);
    end;
  end;
  Form1.BlobDS.DataSet:= Blobs;
  Blobs.Active:= True;
end;

procedure TForm1.ListBox1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  Form1Done := True;
end;

initialization

Form1Done := False;

Copy Code

{
The following code sets the DataSource for a DBGrid
component in Form2 to the currently selected data source in
a list provided in Form1. This allows users to specify the
desired information in Form1, and then move to Form2 to view
the information. Select an item in the listbox and then
activate Form2 by clicking in it. Also, set the visible property
of Form2 to true.
}
procedure TForm2.FormActivate(Sender: TObject);
begin
  if (Form1Done) then
  begin
    DBGrid2.DataSource :=
      Form1.ListBox1.Items.Objects[Form1.ListBox1.ItemIndex] as TDataSource;
    DBNavigator2.DataSource :=
      Form1.ListBox1.Items.Objects[Form1.ListBox1.ItemIndex] as TDataSource;
  end;
end;