修饰符（动态数组篇）

unit Unit4;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;

type
  TForm4 = class(TForm)
    Button1: TButton;
    Memo1: TMemo;
    procedure Button1Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;


  /// <summary>
  /// 定义一个结构(测试这个结构的动态数组)
  /// </summary>
  TRen = record
    name: string;
    age: Integer;
  end;

var
  Form4: TForm4;

implementation

{$R *.dfm}

procedure abc1(ap: TArray<TRen>);
begin
  ap[0].name := ‘李大嘴1‘;
  ap[0].age := 10;
end;

procedure abc2(const ap: TArray<TRen>);
begin
  ap[0].name := ‘李大嘴2‘;
  ap[0].age := 10;
end;

procedure abc3(var ap: TArray<TRen>);
begin
  ap[0].name := ‘李大嘴3‘;
  ap[0].age := 10;
end;

procedure abc4(out ap: TArray<TRen>);
begin
  SetLength(ap, 3); //因为out的作用主要是输出,所以需要再这里进行分配内存,否则会报错
  //.out 修饰的东西会被当成栈中一个不指向堆中任何数据的空指针.
  ap[0].name := ‘李大嘴4‘;
  ap[0].age := 10;
end;

procedure TForm4.Button1Click(Sender: TObject);
var
  vt: TArray<TRen>;
begin
//  SetLength(vt, 3);
//  vt[0].name := ‘小李飞刀‘;
//  vt[0].age := 18;

  abc4(vt);
  Memo1.Lines.Add(vt[0].name);
  Memo1.Lines.Add(vt[0].age.ToString);

  //动态数组也不需要释放,delphi会自动释放,可以看下面的汇编截图,与接口的引用计数释放方式又不同.
  //ip.Free;
end;

procedure TForm4.FormCreate(Sender: TObject);
begin
  ReportMemoryLeaksOnShutdown := True;
end;

end.