Delphi2010中的泛型

2010已发布很长时间了,口碑还不错,准备用它开发下一项目,但对泛型等新东西的认识还不够,就搜了一下,发现下面这篇文章,还不错,大家一起补补课吧!

C++中的模板、C#等语言中泛型技术,给许多操作不同类型数据的软件人员提供了一个很好的方法。其类型的“可变”性,让许多用过的软件人员所心喜。但是在Delphi 2009以前的版本中,是从来没有的。让许多不会用Delphi中TList的人员,大大的抱怨。如果用好Delphi中TList,其可用性,我个人认为,比其它语言中的泛型好用很多(当然对指针的应用和内存的分配、释放不了解的人除外)。

自从Delphi 2009的发布,给许多喜欢用泛型技术的软件人员,提供了方便。由于Delphi 2009不太稳定,也没有过多的去用其泛型技术。Delphi 2010发布以来,出现许多“Delphi 2010初体验,是时候抛弃Delphi 7了”的话语的满天飞,让我想一看其究竟。

闲话少说,Delphi 2010的泛型单元Generics.Defaults、Generics.Collections;重点还是Generics.Collections单元,其中有TArray泛型类、TList(列表的泛型)、TQueue(队列的泛型)、TStack (栈的泛型)、TDictionary (Hash Table哈希表的泛型)及其上述泛型所对应的TObject的泛型,非常广泛。

简单的泛型类应用:(转)


unit Unit1;

interface

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

type
TForm1 = class(TForm)
    Memo1: TMemo;
    Edit1: TEdit;
    Edit2: TEdit;
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure Button4Click(Sender: TObject);
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

uses Generics.Collections; {Delphi 泛型容器单元}

var
Dictionary: TDictionary;
{定义一个泛型 TDictionary 类, 指定有 Cardinal、string 构成}

{建立}
procedure TForm1.FormCreate(Sender: TObject);
begin
Dictionary := TDictionary.Create;

Memo1.Clear;
Button1.Caption := Button1.Caption + ' 添加';
Button2.Caption := Button2.Caption + ' 删除';
Button3.Caption := Button3.Caption + ' 尝试取值';
Button4.Caption := Button4.Caption + ' 清空';

Edit1.Clear;
Edit2.Clear;
Edit1.NumbersOnly := True;
end;

{释放}
procedure TForm1.FormDestroy(Sender: TObject);
begin
Dictionary.Free;
end;

{添加}
procedure TForm1.Button1Click(Sender: TObject);
var
key: Cardinal;
value: string;
str: string;
k,v: Boolean;
begin
key := StrToIntDef(Edit1.Text, 0);
value := Edit2.Text;
if value = '' then value := 'Null';

k := Dictionary.ContainsKey(key);     {Key 是否存在}
v := Dictionary.ContainsValue(value); {Value 是否存在}

if not k then
begin
    Dictionary.Add(key, value);
    Memo1.Lines.Add(Format('%d=%s', [key, value])); {同步显示}
end;

if k and not v then
begin
    str := Format('key 已存在: %d=%s; 是否修改其值?', [key, Dictionary[key]]);
    if MessageBox(0, PChar(str), '提示', MB_OKCANCEL or MB_ICONQUESTION) = mrOk then
    begin
      //Dictionary[key] := value; {Dictionary[key] = Dictionary.Item[key]}
      Dictionary.AddOrSetValue(key, value);       {也可使用上一句}
      Memo1.Lines.Values[IntToStr(key)] := value; {同步显示}
    end;
end;

if k and v then
begin
    str := Format('%d=%s 已存在, 不能重复添加', [key, value]);
    MessageBox(0, PChar(str), '错误', MB_OK + MB_ICONHAND);
end;

Text := IntToStr(Dictionary.Count);
end;

{删除: Remove}
procedure TForm1.Button2Click(Sender: TObject);
var
key: Integer;
i: Integer;
begin
key := StrToIntDef(Edit1.Text, 0);

if not Dictionary.ContainsKey(key) then
begin
    ShowMessageFmt('key: %d 不存在', [key]);
    Exit;
end;

Dictionary.Remove(key);
Text := IntToStr(Dictionary.Count);

{同步显示}
i := Memo1.Lines.IndexOfName(IntToStr(key));
if i > -1 then Memo1.Lines.Delete(i);
end;

{尝试取值: TryGetValue}
procedure TForm1.Button3Click(Sender: TObject);
var
key: Integer;
value: string;
begin
key := StrToIntDef(Edit1.Text, 0);
if Dictionary.TryGetValue(key, value) then
    ShowMessageFmt('key: %d 已存在, 其值是: %s', [key, value])
else
    ShowMessageFmt('key: %d 不存在', [key])
end;

{清空: Clear}
procedure TForm1.Button4Click(Sender: TObject);
begin
Dictionary.Clear;
Text := IntToStr(Dictionary.Count);
Memo1.Clear; {同步显示}
end;

end.

自定义泛型应用:(转)

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 = 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;
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;
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;
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;
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;
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]));
end;

end.