C++ 的初始化方式可以分成很多種， 七種 Initializer ：
- Default initialization
- Value initialization, e.g. std::string s{};
- Direct initialization, e.g. std::string s("hello");
- Copy initialization, e.g. std::string s = "hello";
- List initialization, e.g. std::string s{'a', 'b', 'c'};
- Aggregate initialization, e.g. char a[3] = {'a', 'b'};
- Reference initialization, e.g. char& c = a[0];
兩種 Static initialization：
- Static initialization
- Dynamic initialization
兩種 Dynamic non-local initialization：
- Ordered dynamic initialization
- Unordered dynamic initialization
兩種 Class member initialization：
- Member initializer list
- in-class brace-or-equal initializer