Delphi 2009 泛型容器单元(Generics.Collections)[4]: TDictionary<T>-木庄网络博客

本文整理自网络，侵删。
 TDictionary 类似哈希表.

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;
    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 2009 新增的泛型容器单元}

var
  Dictionary: TDictionary<Cardinal,string>;  
  {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<Cardinal,string>.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.
Delphi 2009 泛型容器单元(Generics.Collections)[4]: TDictionary<T>

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