-> weak_pointers and its methods.

Author: aryanjain28

notes_3_smart_pointers.cpp

@@ -47,8 +47,11 @@ int main()
     // Meaning, only one 'unique pointer' can point to a
     // variable's address. If we try to assign a different
     // pointer to point the same variable. It gives error.
+    // We can move the ownership of one unique-pointer to another,
+    // using the move() method. However, the first pointer will be
+    // deallocated.
 
-    // SHARED POINERS.
+    // SHARED POINTERS.
     // Shared pointers, are the smart pointer that are basically
     // opposite of the unique pointers. Meaning, multiple shared
     // pointers can point towards the same memory address.

notes_4_smart_pointers_practice.cpp

@@ -0,0 +1,61 @@
+#include <iostream>
+#include <memory>
+
+using namespace std;
+
+int main()
+{
+    auto un_pointer_1 = make_unique<int>(516);
+
+    cout << "un_pointer_1: " << un_pointer_1.get() << endl;
+    cout << "*un_pointer_1: " << *un_pointer_1 << endl;
+
+    // auto un_pointer_2 = un_pointer_1;
+    auto un_pointer_2 = move(un_pointer_1);
+
+    cout << "un_pointer_1: " << un_pointer_1.get() << endl;
+    // cout << "*un_pointer_1: " << *un_pointer_1 << endl;
+
+    cout << "un_pointer_2: " << un_pointer_2.get() << endl;
+    cout << "*un_pointer_2: " << *un_pointer_2 << endl;
+
+    shared_ptr<int> sh_pointer_1 = make_shared<int>(325789);
+
+    cout << "sh_pointer_1: " << sh_pointer_1.get() << endl;
+    cout << "*sh_pointer_1: " << *sh_pointer_1 << endl;
+
+    cout << "sh_pointer_1.unique(): " << sh_pointer_1.unique() << endl; // true
+
+    // WOW!! Until a shared_pointer has one owner we can move the,
+    // ownership of unique pointer to the shared pointer.
+    sh_pointer_1 = move(un_pointer_2);
+
+    auto sh_pointer_2 = sh_pointer_1;
+
+    cout << "sh_pointer_2: " << sh_pointer_2.get() << endl;
+    cout << "*sh_pointer_2: " << *sh_pointer_2 << endl;
+
+    cout << "sh_pointer_1.use_count(): " << sh_pointer_1.use_count() << endl;
+    cout << "sh_pointer_1.unique(): " << sh_pointer_1.unique() << endl; // false
+
+    cout << endl
+         << endl;
+
+    weak_ptr<int> wk_pointer = sh_pointer_1;
+
+    cout << "wk_pointer.expired(): " << wk_pointer.expired() << endl;     // false
+    cout << "wk_pointer.use_count(): " << wk_pointer.use_count() << endl; // 2
+
+    sh_pointer_1.reset();
+    cout << "wk_pointer.expired(): " << wk_pointer.expired() << endl;     // false
+    cout << "wk_pointer.use_count(): " << wk_pointer.use_count() << endl; // 1
+
+    sh_pointer_2.reset();
+    cout << "wk_pointer.expired(): " << wk_pointer.expired() << endl;     // true
+    cout << "wk_pointer.use_count(): " << wk_pointer.use_count() << endl; // 0
+
+    // shared_pointer.expired() -> provides status of that shared pointer.
+    // weak_pointer.expired() -> provides status of that all the shared pointer.
+
+    return 1;
+}