question

Mischa Spelt avatar image
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Mischa Spelt asked anthony.johnson commented

Returning string from C++ user command

I'm importing an old (7.x) DLL to 17.0 and running into some problems with user commands returning a string. We used to write functions like

  1. visible double DLL_GetDateTimeString( FLEXSIMINTERFACE )
  2. {
  3.   stringreturn( "Hello world!" );
  4.   return 0;
  5. }

but that does not seem to work anymore. The documentation states that as of FlexSim 2016 one can "simply" return a string from the user command, but I tried a couple of options such as 

  1. visible std::string DLL_GetDateTimeString( FLEXSIMINTERFACE )
  2. {
  3.   return std::string("Hello world!");
  4. }

and

  1. visible char* DLL_GetDateTimeString( FLEXSIMINTERFACE )
  2. {
  3.   std::string result = "Hello world!";
  4.   return apchar( result );
  5. }

or

  1. visible const char* DLL_GetDateTimeString( FLEXSIMINTERFACE )
  2. {
  3.   std::string result = "Hello world!";
  4.   return result.c_str();
  5. }

but they break the stack or give me nonsense output, respectively.

Could you provide an example of how to return strings from a DLL function in version 2017?

FlexSim 17.0.0
user commandc++stringdll functions
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1 Answer

Phil BoBo avatar image
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Phil BoBo answered anthony.johnson commented Best Answer

Change your function definition to return a Variant:

  1. __declspec(dllexport) Variant DLL_GetDateTimeString(FLEXSIMINTERFACE)
  2. {
  3.   return std::string("Hello world!");
  4. }


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