Delphi – E2079 Procedure NEW needs constructor

Posted by AbundantCode

This error message is issued when an identifier given in the parameter list to New is not a constructor.

program Produce;

type
  PMyObject = ^TMyObject;
  TMyObject = object
  F: Integer;
  constructor Init;
  destructor Done;
  end;

constructor TMyObject.Init;
begin
  F := 42;
end;

destructor TMyObject.Done;
begin
end;

var
  P: PMyObject;

begin
  New(P, Done);              (*<-- Error message here*)
end.

By mistake, we called New with the destructor, not the constructor.

program Solve;

type
  PMyObject = ^TMyObject;
  TMyObject = object
  F: Integer;
  constructor Init;
  destructor Done;
  end;

constructor TMyObject.Init;
begin
  F := 42;
end;

destructor TMyObject.Done;
begin
end;

var
  P: PMyObject;

begin
  New(P, Init);
end.

Ensure that the New standard function has a constructor, otherwise it will not work.

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