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Accessing data stored in another Delphi block

In Unit2 of my program, I have the following code:

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;

Then I declare Data: TData in Var.

when i try to do the following in Unit1:

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

I am getting EAccessViolation message. Is there a way to access the data stored in "Data" from Unit1 without error?

+1


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3 answers


Add Data := TData.Create;

to Unit2 section initialization

or change TData to record instead of object. There is nothing wrong with accessing the global Unit2 objects from Unit1 as long as they are properly initialized.



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@ Hendriksen123, initialize the variable Data

before using it? EAccessViolation

is an exception class for invalid memory access errors and usually occurs when your code is trying to access an object that has not been created (initialized) or has already been destroyed.

try using Data := TData.Create;



and then you can use Data

var.

+1


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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.

It works

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