指针问题(100分)

我定义了一个记录类型的数据，然后用一个指针指向它，但是通过指针读取数据的时候会出错，提示“Project Project1.exe raised exception class EAccessViolation with message "Access Violation at address 0040368A in Module 'Project1.exe'.Read address 0013FFDA".Process stopped”，大家帮忙看看怎么回事啊
-------------------------------------------------------------------------------
unit Unit11;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;

type
TForm1 = class(TForm)
Edit1: TEdit;
Button1: TButton;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

TCoinsRec = record
quarters,
pennies :word;
end;
PCoinsRec = ^TCoinsRec;

var
Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
CoinsRec : PCoinsRec;
begin
With CoinsRec^ do
begin
quarters := 10;
pennies := 20;
end;

With CoinsRec^ do
Form1.Edit1.Text := InttoStr(quarters);

Dispose(CoinsRec);
end;
end.

------------------------------------------------------------------------------

你还没有为指针分配内存呢

new(CoinsRec);
With CoinsRec^ do
begin
quarters := 10;
pennies := 20;
end;

var
CoinsRec : PCoinsRec;
begin
New(CoinsRec)
//!!!!!!!!!!!
With CoinsRec^ do
begin
quarters := 10;
pennies := 20;
end;
With CoinsRec^ do
Form1.Edit1.Text := InttoStr(quarters);
Dispose(CoinsRec);
end;
指针只是个数字标识,你得给它分配空间,它指向的内容才可访问

unit Unit1;

interface

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

type
TForm1 = class(TForm)
Button1: TButton;
Edit1: TEdit;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

TCoinsRec = record
quarters,
pennies :word;
end;
PCoinsRec = ^TCoinsRec;

var
Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
CoinsRec : PCoinsRec;
begin
GetMem(CoinsRec,Sizeof(TCoinsRec));
try
with CoinsRec^ do
begin
quarters := 10;
pennies := 20;
end;
With CoinsRec^ do
Form1.Edit1.Text := InttoStr(quarters);
finally
FreeMem(CoinsRec);
end;
end;

end.

你这样写试试,我试过了,可以运行通过

hehe,收到

谢谢