(C++) boost::scoped_ptr

 

boost::scoped_ptr is a smart pointer that deletes the instance it points to when going out of scope.

 

boost::scoped_ptr is similar to std::unique_ptr (C++11) and std::auto_ptr (C++98, depreciated in C++11).

 

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#include <boost/scoped_ptr.hpp> int main() {   const boost::scoped_ptr<MyClass> p(new MyClass);   p->doStuff(); //Hey, the same way of accessing the pointed instance!   //Done, boost::scoped_ptr deletes itself when going out of scope }

 

 

 

 

 

Smart pointers and null

 

Boost smart pointers check for null themselves, so there is no need to check these to be inititialized. In the example below a member variable of a class is requested from an unitialized smart pointer. The program will abort and the runtime error will be shown.

 

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#include <boost/scoped_ptr.hpp> struct Test {   Test(const int x) : m_x(x) {}   const int m_x; }; int main() {   boost::scoped_ptr<Test> p;   p->m_x; //Good: uninitialized pointer detected by Boost }

 

A boost::scoped_ptr can be null, but will check itself for it:

 

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#include <boost/scoped_ptr.hpp> struct Test {   Test(const int x) : m_x(x) {}   const int m_x; }; Test * CreateNullPointer() { return 0; } int main() {   boost::scoped_ptr<Test> p;   p.reset(0); //Valid: boost::scoped_ptr can be empty   p.reset(CreateNullPointer()); //Valid: boost::scoped_ptr can be empty   p->m_x; //Good: uninitialized pointer detected by Boost }

 

 

 

 

 

References

 

1. Scott Meyers. Effective C++ (3rd edition). ISBN:0-321-33487-6. 2005. Item 13: 'Use objects to manage resources'
2. Scott Meyers. Effective C++ (3rd edition). ISBN:0-321-33487-6. 2005. Item 17: 'Store newed objects in smart pointers in standalone statements'