Delphi 2009 中的泛型

本例效果图:

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代码文件:

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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:

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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