The factory pattern provides an object that allocates resources with a means to change the types that the object allocates. To better understand how this pattern works and why it is so useful, let's look at the following example:
class know_it_all{public: auto ask_question(const char *question) { (void) question; return answer("The answer is: 42"); }};
We start, as shown in the preceding code, with a class called know_it_all that provides an answer when asked a question. In this particular case, no matter what question is asked, it always returns the same answer. The answer is defined as the following:
class answer{ std::string m_answer;public: answer(std::string str) : m_answer{std::move(str)} { }};
As shown in the preceding, ...
