An os_function is a generic function pointer class which can be specified with up to ten template parameters. The first template argument specifies the class which the function is a member of. If the function is not a member of any class or is a static member, then os_no_member should be used. The second template argument specifies the return type. The remaining template arguments are optional. An os_function can encapsulate functions, static methods, regular methods, or constant methods. If the function operator is invoked on an os_function before its function pointer is set, then an exception will be thown.

The following example illustrates the usefulness of the os_function class. Four generic function pointers are created. One referencing a function, one referencing a method, one for masquerading as another objects method, and one to illustrate safety.

Example <ospace/helper/examples/genfunc1.cpp>


  #include <iostream>
#include <string>
#include <ospace/helper.h>


void print( os_string str )
  {
  cout << "using print function to print: " << str << endl;
  };


class adder
  {
  public:
    adder() : num_( 0 ) {}
    void add( int num )
      {
      num_ += num;
      cout << "my num is now: " << num_ << endl;
      }

    int num_;
  };


template< class Function >
class aggregator
  {
  public:
    aggregator( Function func ) : func_( func ) {}

    Function func_;
  };



int
main()
  {
  try
    {
    os_function< os_no_object, void, os_string > f1( &print );
    f1( "hello" );

    adder addr;
    addr.add( 1 );

    os_function< adder, void, int > f2( &addr, &adder::add );
    f2( 2 );

    aggregator< os_function< adder, void, int > >
      aggregate
        (
        os_function< adder, void, int >( &addr, &adder::add )
        );
    aggregate.func_( 3 );

    os_function< os_no_object, void > f4;
    f4();
    }
  catch ( os_helper_toolkit_error& e )
    {
    cout << "Caught os_helper_toolkit_error : " << endl;
    cout << '\t' << e.what() << endl;
    cout << '\t' << e.description( e.code() ) << endl;
    }

  return 0;
  }

using print function to print: hello
my num is now: 1
my num is now: 3
my num is now: 6
Caught os_helper_toolkit_error :
        function object does not reference a function or method
        Invalid function call.

Generic Function Pointer

Example <ospace/helper/examples/genfunc1.cpp>