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Why is this an issue?

  When objects are freed, the Destroy destructor method is called.
  Destroy must be an override (or virtual) method.


  All classes inherit from TObject, which declares a virtual Destroy
  method, and should override this method to provide their own implementation.


  Not naming the destructor Destroy will cause it not to be called when the object
  is freed. The same thing happens if Destroy is not an override, because
  the destructor is invoked polymorphically when the object is freed.

How to fix it

  Ensure the destructor is named Destroy and marked with the override
  directive.

type
  TNode = class(TObject)
  private
    FChildNode: TNode;
  public
    destructor CustomDestroy;
  end;

destructor TNode.CustomDestroy;
begin
  FChildNode.Free;
end;

type
  TNode = class(TObject)
  private
    FChildNode: TNode;
  public
    destructor Destroy; override;
  end;

destructor TNode.Destroy;
begin
  FChildNode.Free;
  inherited;
end;


  Note that in the "before" case above, FChildNode.Free would not call the destructor
  on TNode, causing a memory leak.

Resources

  
    
      RAD Studio documentation: Methods (Delphi)