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POHow to pass "nil" constant to the untyped parameter?
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  1. POHow to pass "nil" constant to the untyped parameter?
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    copied!<p>is it possible to pass nil as an undeclared constant to the untyped parameter of some function? I have functions like these and I would like to pass some constant to the <code>Data</code> parameter to satisfy the compiler. Internally I'm deciding by the Size parameter. I know I can use Pointer instead of untyped parameter but it's much more comfortable for my case.</p> <p>Now I'm getting <code>E2250 There is no overloaded version of 'RS232_SendCommand' that can be called with these arguments</code></p> <pre><code>function RS232_SendCommand(const Command: Integer): Boolean; overload; begin // is it possible to pass here an undeclared constant like nil in this example? Result := RS232_SendCommand(Command, nil, 0); end; function RS232_SendCommand(const Command: Integer; const Data; const Size: Integer): Boolean; overload; begin ... end; </code></pre> <p>This works, but I would be glad if I could leave the variable declaration.</p> <pre><code>function RS232_SendCommand(const Command: Integer): Boolean; overload; var Nothing: Pointer; begin Result := RS232_SendCommand(Command, Nothing, 0); end; </code></pre> <hr> <p>Solution is to use somthing like this.</p> <pre><code>function RS232_SendCommand(const Command: Integer): Boolean; overload; begin // as the best way looks for me from the accepted answer to use this Result := RS232_SendCommand(Command, nil^, 0); // or it also possible to pass an empty string constant to the untyped parameter // without declaring any variable Result := RS232_SendCommand(Command, '', 0); end; </code></pre> <p>I'm doing this because some of my commands have a data sent after command transmission.</p> <p>Thanks for the help</p>
 

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