Constructor initialization list

The constructor initialization list is sometimes necessary. Although the constructor is divided into initialization and computing stages, it is more efficient to use the initialization constructor list. This is one of them and must be used in some cases. The following is an example,

1 class Foo 2 {3 Public: 4 Foo (int x, int y): A (x), B (y) {} 5 6 private: 7 int; 8 int B; 9}; 10 11 class bar12 {13 public: 14 bar (): Foo (10, 10) {} 15 private: 16 Foo; 17 };

The type of member Foo does not have a default constructor. Calling the default constructor in the initialization phase will fail. If there is no bar constructor initialization list.

Therefore, you must use the initialization list for any const, reference type members, and members without the default constructor class type.

Constructor initialization list