Neargye/scope_guard

References

• Andrei Alexandrescu "Systematic Error Handling in C++"
• Andrei Alexandrescu “Declarative Control Flow"

Examples

1、Scope Guard on exit

std::fstream file("test.txt");
SCOPE_EXIT{ file.close(); }; // File closes when exit the enclosing scope or errors occur.

2、Scope Guard on fail

persons.push_back(person); // Add the person to db.
SCOPE_FAIL{ persons.pop_back(); }; // If errors occur, we should roll back.

3、Scope Guard on success

person = new Person{/*...*/};
// ...
SCOPE_SUCCESS{ persons.push_back(person); }; // If no errors occur, we should add the person to db.

4、Custom Scope Guard

persons.push_back(person); // Add the person to db.

MAKE_SCOPE_EXIT(scope_exit) { // Following block is executed when exit the enclosing scope or errors occur.
  persons.pop_back(); // If the db insertion fails, we should roll back.
};
// MAKE_SCOPE_EXIT(name) {action} - macro is used to create a new scope_exit object.
scope_exit.dismiss(); // An exception was not thrown, so don't execute the scope_exit.

persons.push_back(person); // Add the person to db.

auto scope_exit = make_scope_exit([]() { persons.pop_back(); });
// make_scope_exit(A&& action) - function is used to create a new scope_exit object. It can be instantiated with a lambda function, a std::function<void()>, a functor, or a void(*)() function pointer.
// ...
scope_exit.dismiss(); // An exception was not thrown, so don't execute the scope_exit.

4、With Scope Guard

std::fstream file("test.txt");
WITH_SCOPE_EXIT({ file.close(); }) { // File closes when exit the enclosing with scope or errors occur.
  // ...
};

Read code

scope_guard/include/scope_guard.hpp

它的实现和SergiusTheBest/ScopeExit比较类似，都借助了macro、lambda。显然它的实现是更加完备的。它采用了policy-based design