我不能理解的语法
class_name: class_ptr_1(nullptr), class_ptr_2(nullptr) {}
It seems you mean
class_name() : class_ptr_1(nullptr), class_ptr_2(nullptr) {} ^^^
It is a constructor definition with a mem-initializer list. That is the class data members class_ptr_1 and class_ptr_2 are initialized in the mem-initializer list.
class_ptr_1
class_ptr_2
It seems you mean
It is a constructor definition with a mem-initializer list. That is the class data members
class_ptr_1andclass_ptr_2are initialized in the mem-initializer list.