NamedParameterByThis.cpp

/**
 * \file  NamedParameterByThis.cpp
 * \brief Solve order of the parameters problem
 *
 * Change the function's parameters to methods of a newly created class, where all these methods
 * return *this by reference. Then you simply rename the main function into a parameterless "do-it"
 * method on that class
 *
 * When a function takes many parameters, the programmer has to remember the types and the order
 * in which to pass them. Also, default values can only be given to the last parameters,
 * so it is not possible to specify one of the later parameters and use the default value
 * for former ones. Named parameters let the programmer pass the parameters to a function in any
 * order and they are distinguished by a name. So the programmer can explicitly pass all the needed
 * parameters and default values without worrying about the order used in the function declaration.
 */


#include <StdStream/StdStream.h>
#include <StdTest/StdTest.h>
#include <Stl.h>
//--------------------------------------------------------------------------------------------------
class X
{
public:
	// non-const function
	X &
	setA(const int i)
	{
		_a = i;
		return *this;
	}

	// non-const function
	X &
	setB(const char c)
	{
		_b = c;
		return *this;
	}

	static
	X construct()
	{
		return X();
	}

private:
	int  _a {};
	char _b {};

	// Initialize with default values, if any.
	X() :
		_a{-999},
		_b{'C'}
	{
	}

	friend
	std::ostream &operator << (std::ostream &os, const X &x);
};
//-------------------------------------------------------------------------------------------------
std::ostream &
operator << (std::ostream &os, const X &x)
{
	os
		<< "{" << x._a << ", " << x._b << "}";

	return os;
}
//--------------------------------------------------------------------------------------------------
int main(int, char **)
{
	const auto &x = X::construct()
						.setA(10)
						.setB('Z');

	std::cout << STD_TRACE_VAR(x) << std::endl;

    return EXIT_SUCCESS;
}
//--------------------------------------------------------------------------------------------------


#if OUTPUT

x: {10, Z}

#endif