Thread-safe way to increment and return an integer in Delphi

Question

In a single-threaded application I use code like this:

Interface
    function GetNextUID : integer;
Implementation
    function GetNextUID : integer;
    const
      cUID : integer = 0;
    begin
      inc( cUID );
      result := cUID;
    end;

This could of course be implemented as a singleton object, etc. - I'm just giving the simplest possible example.

Q: How can I modify this function (or design a class) to achieve the same result safely from concurrent threads?

Answer 1

The easiest way would probably be to just call InterlockedIncrement to do the job.

Answer 2

You can use the Interlocked* functions:

    function GetNextUID : integer;
    {$J+} // Writeble constants
    const
      cUID : integer = 0;
    begin
      Result := InterlockedIncrement(cUID);
    end;