Add unique_ptr video

README.md

@@ -12,6 +12,7 @@ James and his team are available for consulting, contracting, code reviews, and
 
 | N | Code | Video | 
 | -- | --- |--- |
+| 121 | [src](videos/121_unique_ptr) | [unique_ptr: C++'s simplest smart pointer](https://youtu.be/AmjoK55h68Y) |
 | 120 | [src](videos/120_python_ternary_operator) | [Does Python have a ternary operator?](https://youtu.be/zjwhh2MEa0Q) |
 | 119 | [src](videos/119_more_nooby_python_habits) | [21 MORE nooby Python habits](https://youtu.be/E8NijUYfyus) |
 | 118 | [src](videos/118_strings_and_bytes) | [str vs bytes in Python](https://youtu.be/EimoZHDcQMA) |

videos/121_unique_ptr/.clang-format

@@ -0,0 +1,5 @@
+---
+BasedOnStyle: Google
+IndentWidth: 4
+---
+

videos/121_unique_ptr/CMakeLists.txt

@@ -0,0 +1,10 @@
+cmake_minimum_required(VERSION 3.16...3.23)
+
+project(UNIQUE_PTR_EXAMPLE)
+
+add_executable(main main.cpp)
+set_target_properties(
+    main PROPERTIES
+    CXX_STANDARD 20
+    CXX_EXTENSIONS OFF
+)

videos/121_unique_ptr/main.cpp

@@ -0,0 +1,131 @@
+#include <iostream>
+#include <memory>
+#include <utility>
+#include <vector>
+
+template <class T>
+class unique_ptr {
+   public:
+    unique_ptr() noexcept : unique_ptr{nullptr} {}
+    explicit unique_ptr(T *ptr) noexcept : m_ptr{ptr} {}
+
+    unique_ptr(const unique_ptr &) = delete;
+    unique_ptr &operator=(const unique_ptr &) = delete;
+
+    unique_ptr(unique_ptr &&other) noexcept : m_ptr{other.release()} {}
+
+    unique_ptr &operator=(unique_ptr &&other) noexcept {
+        if (this != &other) {
+            reset(other.release());
+        }
+        return *this;
+    }
+
+    explicit operator bool() const noexcept { return static_cast<bool>(m_ptr); }
+
+    T *get() const noexcept { return m_ptr; }
+    T *operator->() const noexcept { return m_ptr; }
+    T &operator*() const noexcept { return *m_ptr; }
+
+    T *release() noexcept { return std::exchange(m_ptr, nullptr); }
+
+    void reset(T *ptr = nullptr) noexcept {
+        T *old = std::exchange(m_ptr, ptr);
+        if (old) {
+            delete old;
+        }
+    }
+
+    ~unique_ptr() noexcept {
+        if (m_ptr) {
+            delete m_ptr;
+        }
+    }
+
+   private:
+    T *m_ptr;
+};
+
+template <class T, class... Args>
+unique_ptr<T> make_unique(Args &&...args) {
+    return unique_ptr<T>(new T(std::forward<Args>(args)...));
+}
+
+struct Widget {
+    int val;
+
+    explicit Widget(int val) : val{val} {
+        std::cout << "ctor: " << val << '\n';
+    }
+
+    virtual ~Widget() noexcept { std::cout << "dtor: " << val << '\n'; }
+};
+
+void use_widget(const Widget *w) {
+    std::cout << "yep, that's a widget: " << w->val << '\n';
+}
+
+void use_widget(const Widget &w) {
+    std::cout << "yep, that's a widget: " << w.val << '\n';
+}
+
+void vector_raw_example() {
+    std::vector<Widget *> widgets;
+    const std::size_t count = 5;
+    widgets.reserve(count);
+    for (std::size_t i = 0; i < count; ++i) {
+        widgets.push_back(new Widget(i));
+    }
+
+    for (const auto &widget : widgets) {
+        use_widget(widget);
+    }
+
+    delete widgets.back();
+    widgets.pop_back();
+
+    Widget *last = widgets.back();
+    widgets.pop_back();
+
+    std::cout << "last element was " << last->val << '\n';
+
+    delete last;
+
+    for (std::size_t i = 0; i < widgets.size(); ++i) {
+        delete widgets[i];
+    }
+}
+
+void vector_example() {
+    std::vector<unique_ptr<Widget>> widgets;
+    const std::size_t count = 5;
+    widgets.reserve(count);
+    for (std::size_t i = 0; i < count; ++i) {
+        widgets.push_back(unique_ptr<Widget>(new Widget(i)));
+        // widgets.push_back(make_unique<Widget>(i));
+    }
+
+    for (const auto &widget : widgets) {
+        use_widget(widget.get());
+        use_widget(*widget);
+    }
+
+    widgets.pop_back();  // automatically deleted
+
+    unique_ptr<Widget> last = std::move(widgets.back());
+    widgets.pop_back();
+
+    std::cout << "last element was " << last->val << '\n';
+}
+
+int main() {
+    int *xp = new int(42);
+    *xp = 0;
+    delete xp;
+
+    auto yp = std::make_unique<int>(42);
+    *yp = 0;
+
+    vector_example();
+    return 0;
+}