Delphi 2009 中的泛型

本例效果图:

代码文件:

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Memo1: TMemo;
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    Button5: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure Button4Click(Sender: TObject);
    procedure Button5Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

type
  TArr<T> = array[0..9] of T; {定义一个泛型数组}
  {虽然大家习惯用 T 来泛指其他类型, 但使用其他合法的标识符也是可以的}

{用作 Integer}
procedure TForm1.Button1Click(Sender: TObject);
var
  Arr: TArr<Integer>;
  i: Integer;
begin
  for i := Low(Arr) to High(Arr) do
    Arr[i] := i * i;

  Memo1.Clear;
  for i := Low(Arr) to High(Arr) do
    Memo1.Lines.Add(Format('Arr[%d] = %d', [i, Arr[i]]));
end;

{用作 string}
procedure TForm1.Button2Click(Sender: TObject);
var
  Arr: TArr<string>;
  i: Integer;
begin
  for i := Low(Arr) to High(Arr) do
    Arr[i] := StringOfChar(Char(i+97), 3);

  Memo1.Clear;
  for i := Low(Arr) to High(Arr) do
    Memo1.Lines.Add(Format('Arr[%d] = %s', [i, Arr[i]]));
end;

{用作 Single}
procedure TForm1.Button3Click(Sender: TObject);
var
  Arr: TArr<Single>;
  i: Integer;
begin
  for i := Low(Arr) to High(Arr) do
    Arr[i] := 100 / (i+1);

  Memo1.Clear;
  for i := Low(Arr) to High(Arr) do
    Memo1.Lines.Add(Format('Arr[%d] = %f', [i, Arr[i]]));
end;

{用作记录 TPoint}
procedure TForm1.Button4Click(Sender: TObject);
var
  Arr: TArr<TPoint>;
  i: Integer;
begin
  for i := Low(Arr) to High(Arr) do
    Arr[i] := Point(i, i*2);

  Memo1.Clear;
  for i := Low(Arr) to High(Arr) do
    Memo1.Lines.Add(Format('Arr[%d] = (%d,%d)', [i, Arr[i].X, Arr[i].Y]));
end;

{用作类 TButton}
procedure TForm1.Button5Click(Sender: TObject);
var
  Arr: TArr<TButton>;
  i: Integer;
begin
  for i := Low(Arr) to High(Arr) do
  begin
    Arr[i] := TButton.Create(Self);
    Arr[i].Name := Concat('Btn', IntToStr(i+1));
  end;

  Memo1.Clear;
  for i := Low(Arr) to High(Arr) do
    Memo1.Lines.Add(Format('Arr[%d] is %s', [i, Arr[i].Name]));

  for i := Low(Arr) to High(Arr) do Arr[i].Free;
end;

end.

窗体文件:

object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 158
  ClientWidth = 232
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  PixelsPerInch = 96
  TextHeight = 13
  object Button1: TButton
    Left = 136
    Top = 6
    Width = 75
    Height = 25
    Caption = 'Button1'
    TabOrder = 0
    OnClick = Button1Click
  end
  object Memo1: TMemo
    Left = 0
    Top = 0
    Width = 113
    Height = 158
    Align = alLeft
    Lines.Strings = (
      'Memo1')
    ScrollBars = ssVertical
    TabOrder = 1
    ExplicitHeight = 167
  end
  object Button2: TButton
    Left = 136
    Top = 36
    Width = 75
    Height = 25
    Caption = 'Button2'
    TabOrder = 2
    OnClick = Button2Click
  end
  object Button3: TButton
    Left = 136
    Top = 66
    Width = 75
    Height = 25
    Caption = 'Button3'
    TabOrder = 3
    OnClick = Button3Click
  end
  object Button4: TButton
    Left = 136
    Top = 96
    Width = 75
    Height = 25
    Caption = 'Button4'
    TabOrder = 4
    OnClick = Button4Click
  end
  object Button5: TButton
    Left = 136
    Top = 126
    Width = 75
    Height = 25
    Caption = 'Button5'
    TabOrder = 5
    OnClick = Button5Click
  end
end