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Boost - Scoped pointer

Here is the first article about Boost libraries features. I am starting that new series of articles with explanation of scoped_ptr - one of the Boost smart pointers.

scoped_ptr is smart pointer that is the only owner of dynamically allocated object and is automatically freed allocated memory when destructor of scoped_ptr is called.

See example below:
Output of this example is:

In point I and II we are defining two scoped_ptr pointers - one for int and one for Test (custom class) object.

Notice comment marked as Ia. That is impossible operation for scoped_ptr. It is trying to assign ownership of allocated object to second pointer. scoped_ptr does not allow it. It have to be sole owner of its object.

Point III shows how we can assign new values to object which refers to scoped_ptr. We can use dereference operator (operator*) as for normal pointers (this operator is overloaded in Boost smart pointers) as well as use get() function implemented to Boost smart pointers.

Point IV shows how to use reset function to replace object which is being pointed by scoped_ptr. We can use reset() function for it. After using that function new object will be allocated and old object will be freed automatically. Therefore you can see text: "Constructor of Test class: 2 Destructor of Test class: 1" in the output text.

Take a special look at point V. This is place where we are exiting area of visibility of our scoped_ptr objects. In that place memory allocated for those pointers will be automatically freed. We do not have to use delete function like for normal pointers.

Smart pointers automatically free memory associated with dynamically allocated object which is being pointed by them while scoped_ptr destructor is being invoked.

Code of this example can be downloaded from here: https://github.com/xmementoit/CppAdventureExamples/tree/master/boost/scopedPointer


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