Delphi如何动态设置内存映像中数组大小

Question

unit Unit1;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;type
  TForm3 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;var
  Form3: TForm3;implementation{$R *.dfm}procedure TForm3.Button1Click(Sender: TObject);
type
  TShared = record
    keys:array of String[255];
  end;
  PShared = ^TShared;
const
  PMEMF='afkgjsl';
var
  Shared:PShared;
  MapHandle: THandle;
  i:Integer;
begin
    SetLength(Shared^.keys,4);   //到这里出错，
    MapHandle:=OpenFileMapping(FILE_MAP_ALL_ACCESS,False, PMEMF);
    if MapHandle=0 then
    begin
      MapHandle := CreateFileMapping($FFFFFFFF, nil,PAGE_READWRITE,0,SizeOf(TShared),PMEMF);
    end;
    if MapHandle<>0 then
      begin
      Shared:=MapViewOfFile(MapHandle,FILE_MAP_ALL_ACCESS,0,0,0);
      end;
    Shared^.keys[0]:='abcd';
    Shared^.keys[1]:='efgh';
    Shared^.keys[2]:='hijkl';
    Shared^.keys[3]:='mnopq';
end;end.Shared^.keys 是需要动态确定的，请问如何设置！

Answer 1

Shared:PShared;是一个指针，你创建了吗？因为你没创建，所以出错

Answer 2

new(Shared);//使用前先分配下内存SetLength(Shared^.keys,4); //到这里出错，
MapHandle:=OpenFileMapping(FILE_MAP_ALL_ACCESS,False, PMEMF);

Answer 3

 你好，我需要将Shared^.keys共享，在其它进程要读取其值，
请帮我改写下代码，

Answer 4

unit Unit1;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;type
  TForm3 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;type
  TShared = record
    keys:array of String[255];
  end;
  PShared = ^TShared;
var
  Form3: TForm3;implementation{$R *.dfm}procedure TForm3.Button1Click(Sender: TObject);
const
  PMEMF='afkgjsl';
var
  Shared:PShared;
  MapHandle: THandle;
begin
    new(Shared);
    SetLength(Shared^.keys,4);
    MapHandle:=OpenFileMapping(FILE_MAP_ALL_ACCESS,False, PMEMF);
    if MapHandle=0 then
    begin
      MapHandle := CreateFileMapping($FFFFFFFF, nil,PAGE_READWRITE,0,SizeOf(TShared),PMEMF);
    end;
    if MapHandle<>0 then
      begin
      Shared:=MapViewOfFile(MapHandle,FILE_MAP_ALL_ACCESS,0,0,0);
      end;
    Shared^.keys[0]:='abcd';
    Shared^.keys[1]:='efgh';
    Shared^.keys[2]:='hijkl';
    Shared^.keys[3]:='mnopq';
end;end.读取代码
unit Unit2;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;type
  TForm4 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
type
  TShared = record
    keys:array of String[255];
  end;
  PShared = ^TShared;
var
  Form4: TForm4;implementation{$R *.dfm}procedure TForm4.Button1Click(Sender: TObject);
const
  PMEMF='afkgjsl';
var
  MapHandle: THandle;
  Shared:PShared;
begin
    New(Shared);
    SetLength(Shared^.keys,4);
    MapHandle:=OpenFileMapping(FILE_MAP_ALL_ACCESS,False, PMEMF);
    Shared:=MapViewOfFile(MapHandle,FILE_MAP_ALL_ACCESS,0,0,0);
    ShowMessage(String(Shared^.keys[0]));
    ShowMessage(String(Shared^.keys[1]));
    ShowMessage(String(Shared^.keys[2]));
    ShowMessage(String(Shared^.keys[3]));
end;end.