Suppose you’ve got a user interface class with many user options that you need to set/get at the same time. Here’s one way to implement this:

class CUI{public:  CUI() : m_bOption(false), m_cOption(''), m_iOption(0), m_dOption(0.0){}  //...  void GetOptions(bool bOption, char cOption, int& riOption, double&rdOption)  {    bOption = m_bOption;    cOption = m_cOption;    riOption = m_iOption;    rdOption = m_dOption;  }  void SetOptions(bool bOption, char cOption, int const& riOption, doubleconst& rdOption)  {    m_bOption = bOption;    m_cOption = cOption;    m_iOption = riOption;    m_dOption = rdOption;  }private:  //...  bool m_bOption;  char m_cOption;  int m_iOption;  double m_dOption;};

The problem with this implementation is that when the number of options increases, you need to transfer a larger amount of data as arguments to the getter/setter functions. This is not an efficient way to make use of the program’s stack. The solution is to create an inner structure containing all the options:

#include using namespace std;class CUI{public:  struct SOptions  {    SOptions() : m_bOption(false), m_cOption(''), m_iOption(0),m_dOption(0.0) {}    bool m_bOption;    char m_cOption;    int m_iOption;    double m_dOption;  };  CUI() {}  //...  void GetOptions(SOptions& roOptions)  {    roOptions.m_bOption = m_oOptions.m_bOption;    roOptions.m_cOption = m_oOptions.m_cOption;    roOptions.m_iOption = m_oOptions.m_iOption;    roOptions.m_dOption = m_oOptions.m_dOption;  }  void SetOptions(SOptions const& roOptions)  {    m_oOptions.m_bOption = roOptions.m_bOption;    m_oOptions.m_cOption = roOptions.m_cOption;    m_oOptions.m_iOption = roOptions.m_iOption;    m_oOptions.m_dOption = roOptions.m_dOption;  }private:  //...  SOptions m_oOptions;};