1. Use "=default"
1. Explicitly generate synthetic versions of copy control members
class A {
public:
A() = default;
A(const A &) = default;
A& operator=(const A &) = default;
~A() = default;
};
2. You can only use '=default' for member functions with synthetic versions
- default constructor
- Copy control members (copy constructor, copy assignment operator, destructor, move constructor, move assignment operator)
3. Synthetic functions generated using "=default" are divided into inline and non-inline
class A {
public:
A() = default; // use =default-->inline in class
A(const A &) = default; // use =default-->inline in the class
A& operator=(const A &);
};
A& A::operator=(const A &) = default; // outside the class = default --> not inline
2. Use "=delete"
1. Define the related function as the deleted function
- Deleted function: We declare it, but cannot use it in any way.
2. =delete must appear when the function is first declared
3. You can specify =delete for any function
- The main purpose of the deleted function is to prohibit copying of control members
4. Destructor cannot use "=delete"
5. Example
class A {
public:
A() = default; // use synthetic default constructor
A(const A &) = delete; // prevent copying
A& operator=(const A &) = delete; // prevent assignment
~A() = default; // use synthetic destructor
};