访问存储在另一单元中的数据的Delphi

Question

在UNIT2我的节目的我有以下代码：

TValue = Record
  NewValue,
  OldValue,
  SavedValue : Double;
end; 

TData = Class(TObject)
Public
  EconomicGrowth : TValue;
  Inflation : TValue;
  Unemployment : TValue;
  CurrentAccountPosition : TValue;
  AggregateSupply : TValue;
  AggregateDemand : TValue;
  ADGovernmentSpending : TValue;
  ADConsumption : TValue;
  ADInvestment : TValue;
  ADNetExports : TValue;
  OverallTaxation : TValue;
  GovernmentSpending : TValue;
  InterestRates : TValue;
  IncomeTax : TValue;
  Benefits : TValue;
  TrainingEducationSpending : TValue;
End;

我然后声明数据：TDATA在无功

当我尝试做然而，在1单元执行以下操作：

  ShowMessage(FloatToStr(Unit2.Data.Inflation.SavedValue));

我得到一个EAccessViolation消息。有没有什么办法来访问存储在从1单元“数据”的数据没有得到错误？

Answer 1

...添加到Data := TData.Create; UNIT2的initialization部分，或改变TDATA到记录，而不是一个对象。没有什么内在的错误访问UNIT2的从1单元全局对象，只要他们正确初始化。

Answer 2

@ Hendriksen123，你初始化变量Data使用它之前？该EAccessViolation是无效的内存访问错误的异常类，通常当你的代码试图访问未创建（初始化）或者已经被销毁的对象出现。

尝试使用Data := TData.Create;

和然后可以使用Data变种

Answer 3

unit Unit2;

interface

type
  TValue = Record
    NewValue,
    OldValue,
    SavedValue : Double;
  end;

  TData = Class(TObject)
  Public
    EconomicGrowth : TValue;
    Inflation : TValue;
    Unemployment : TValue;
    CurrentAccountPosition : TValue;
    AggregateSupply : TValue;
    AggregateDemand : TValue;
    ADGovernmentSpending : TValue;
    ADConsumption : TValue;
    ADInvestment : TValue;
    ADNetExports : TValue;
    OverallTaxation : TValue;
    GovernmentSpending : TValue;
    InterestRates : TValue;
    IncomeTax : TValue;
    Benefits : TValue;
    TrainingEducationSpending : TValue;
  End;

procedure InitialiseData (var pData : TData);

implementation

procedure InitialiseData (var pData : TData);
begin
  pData := TData.Create;

  pData.EconomicGrowth.SavedValue := 1.00;

end;

end.

---

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs, Unit2,
  StdCtrls;

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

var
  Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
var
  vData : TData;
begin
  Unit2.InitialiseData(vData);

  ShowMessage(FloatToStr(vData.EconomicGrowth.SavedValue));

end;

end.

---

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