Explicit

Prefixing the explicit keyword to the constructor prevents the compiler from using that constructor for implicit conversions. Example is shown below.

namespace HW
{
/**
 * @class MoneyC
 * @brief
 */
class MoneyC
{
public:
   /**
    * @brief Constructor
    */
   MoneyC();

   /**
    * @brief Constructor
    */
   explicit MoneyC(float iValue);

   /**
    * @brief Destructor
    */
   ~MoneyC() = default;

   /**
    * @brief Set copy constructor as delete to prevent unintentional creation
    */
   //MoneyC(const MoneyC& iValue) = delete;

   float GetAmount(void) const;

   /**
    * @brief Set copy constructor as delete to prevent unintentional creation
    */
   MoneyC(const MoneyC& iValue) = delete;
   /**
    * @brief Set copy assignment as delete to prevent unintentional creation
    */
   const MoneyC& operator=(const MoneyC& iValue) = delete;
private:
   float mAmount;
};

namespace HW
{

MoneyC::MoneyC():mAmount(1.0)
{
}

MoneyC::MoneyC(float iValue):mAmount(iValue)
{
}

float MoneyC::GetAmount(void) const
{
   return this->mAmount;
}

} // end of namespace HW

void DisplayMoneyInfo(const HW::MoneyC& iMoney)
{
   std::cout << "The Amountt of Money is: ";
   std::cout << iMoney.GetAmount() << std::endl;

}

void MoneyTest(void)
{
   std::cout << "===============MoneyTest()==================\n";
   HW::MoneyC money1(4.99f);
   DisplayMoneyInfo(money1);
   DisplayMoneyInfo(4.99f);
   DisplayMoneyInfo((HW::MoneyC)7.99f);
}

When compiling, the error will be indicated.

..\src\Learning.cpp:123:26: error: invalid initialization of reference of type 'const HW::MoneyC&' from expression of type 'float'

DisplayMoneyInfo(4.99f);

If remove the “explicit”, it can be compiled successful.