详测 Generics Collections TDictionary(2): ContainsKey、ContainsValue、AddOrSetValue、TryGetValue

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses Generics.Collections;

procedure TForm1.Button1Click(Sender: TObject);
var
  Dictionary: TDictionary<string,Integer>;
  b: Boolean;
  T: Integer;
begin
  Dictionary := TDictionary<string,Integer>.Create();

  {添加}
  Dictionary.Add('n1', 111);
  Dictionary.Add('n2', 222);
  Dictionary.Add('n3', 333);

  {判断指定的 Key 是否存在}
  b := Dictionary.ContainsKey('n1');
  ShowMessage(BoolToStr(b, True));   {True}
  b := Dictionary.ContainsKey('n4');
  ShowMessage(BoolToStr(b, True));   {False}

  {判断指定的 Value 是否存在}
  b := Dictionary.ContainsValue(111);
  ShowMessage(BoolToStr(b, True));   {True}
  b := Dictionary.ContainsValue(999);
  ShowMessage(BoolToStr(b, True));   {False}

  {使用 AddOrSetValue 时, 如果 Key 存在则替换值; 此时如果用 Add 将发生异常}
  Dictionary.AddOrSetValue('n1', 123);
  ShowMessage(IntToStr(Dictionary['n1'])); {123}

  {使用 AddOrSetValue 时, 如果 Key 不存在则同 Add}
  Dictionary.AddOrSetValue('n4', 444);
  ShowMessage(IntToStr(Dictionary['n4'])); {444}

  {尝试取值}
  if Dictionary.TryGetValue('n2', T) then
    ShowMessage(IntToStr(T)); {222}
  
  Dictionary.Free;
end;

end.