RAII 的妙用

RAII 就是为了防止 e.g 1) malloc 忘了 delete 2) open 忘了 close 3) acquire lock忘了 release

good link 

https://www.tomdalling.com/blog/software-design/resource-acquisition-is-initialisation-raii-explained/

https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#e6-use-raii-to-prevent-leaks

类似 constructor destructor

The basic idea is to represent a resource by a local object, so that the local object's destructor will release the resource. That way, the programmer cannot forget to release the resource.

In other words:

Pointers should be encapsulated in smart pointer classes (see std::auto_ptr, boost::shared_ptr and boost::scoped_ptr for examples).

Handles requiring cleanup should be encapsulated in classes that automatically free/release the handles upon destruction.

RAII can be summarized as follows:

• encapsulate each resource into a class, where
  • the constructor acquires the resource and establishes all class invariants or throws an exception if that cannot be done,
  • the destructor releases the resource and never throws exceptions;
• always use the resource via an instance of a RAII-class that either
  • has automatic storage duration or temporary lifetime itself, or
  • has lifetime that is bounded by the lifetime of an automatic or temporary object

Move semantics make it possible to safely transfer resource ownership between objects, across scopes, and in and out of threads, while maintaining resource safety.