C + + must use an initialization list

1. In an inheritance relationship, the parent class has no default constructor
2. Class type class member variable no default constructor
3. Const type member variable
4. Reference type member variable

Without the initialization list, the default initialization of all member variables before the object invocation constructor is performed, and then the contents of the constructor body are executed, which is not applicable for types that do not have default constructors and variables that need to be assigned when declared. The initialization list is part of the function declaration (the constructor Declaration) and is suitable for those variables that need to be assigned when declared.


From for notes (Wiz)

C + + must use an initialization list