C++ Tutorial 15
In this part of my C++ tutorial I will answer a bunch of questions I have received. I’ll talk about allocating memory with malloc(), Smart Pointers, Regular Pointers, Deallocating Memory, unique_ptr, Difference Between /n and endl, Polymorphic Templates and a whole bunch more.
Like always the heavily commented code follows the video below. For best results print it out and take notes as you watch.
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Code From the Video
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// ---------- C++ Tutorial 15 ---------- // ---------- SMART POINTER EXAMPLE ---------- #include <cstdlib> #include <iostream> #include <string> #include <vector> #include <ctime> #include <numeric> #include <cmath> #include <sstream> #include <iterator> #include <memory> #include <stdio.h> // A Smart pointer is a class that provides the // power of pointers, but also handles the reallocation // of memory when it is no longer required (The pointer // is automatically destroyed) // typedef creates an alias for a more complex type name typedef std::vector<int32_t> intVec; int main() { /* MALLOC EXAMPLE // When you define a primitive type like int or // float you define exactly the amount of space // to set aside // If you need to define how much space to set aside // you could call malloc() and tell it how much // space to set aside and it returns the address to // that memory address int amtToStore; std::cout << "How many numbers do you want to store : "; std::cin >> amtToStore; // Create an int pointer and set aside enough space int * pNums; // Cast the pointer and define how much space to set aside pNums = (int *) malloc(amtToStore * sizeof(int)); // Check if memory was allocated if(pNums != NULL){ int i = 0; // Store values while(i < amtToStore){ std::cout << "Enter a Number : "; std::cin >> pNums[i]; i++; } } std::cout << "You entered these numbers\n"; for(int i = 0; i < amtToStore; i++){ std::cout << pNums[i] << "\n"; } // Delete the pointer delete pNums; */ // Smart Pointer Solution int amtToStore; std::cout << "How many numbers do you want to store : "; std::cin >> amtToStore; // This memory will be automatically reallocated std::unique_ptr<int[]> pNums(new int[amtToStore]); // unique_ptr can only have one owner // so this throws an error // std::unique_ptr<int[]> pNums2 = pNums; // I'll cover how to do this with shared_ptr // in a later tutorial if(pNums != NULL){ int i = 0; // Store values while(i < amtToStore){ std::cout << "Enter a Number : "; std::cin >> pNums[i]; i++; } } std::cout << "You entered these numbers\n"; for(int i = 0; i < amtToStore; i++){ std::cout << pNums[i] << "\n"; } return 0; } // ---------- END SMART POINTER EXAMPLE ---------- // ---------- POLYMORPHIC TEMPLATES ---------- #include <cstdlib> #include <iostream> #include <string> #include <vector> #include <ctime> #include <numeric> #include <cmath> #include <sstream> #include <iterator> #include <memory> // Here I demonstrate how to use templates // polymorphically // Base class all pizzas inherit along with MakePizza // which will be overridden class Pizza{ public: virtual void MakePizza() = 0; }; // The last templates that will be called class NYStyleCrust { public: std::string AddIngredient() { return "Crust so Thin You can See through it\n\n"; } }; class DeepDishCrust { public: std::string AddIngredient() { return "Super Awesome Chicago Deep Dish Crust\n\n"; } }; // End of last templates called // The middle templates called template <typename T> class LotsOfMeat: public T { public: std::string AddIngredient() { return "Lots of Random Meat, " + T::AddIngredient(); } }; template <typename T> class Vegan: public T { public: std::string AddIngredient() { return "Vegan Cheese, Veggies, " + T::AddIngredient(); } }; // End of middle templates called // We inherit from Pizza as well as the initial next template template <typename T> class MeatNYStyle: public T, public Pizza { public: void MakePizza() { std::cout << "Meat NY Style Pizza : " << T::AddIngredient(); } }; template <typename T> class VeganDeepDish: public T, public Pizza { public: void MakePizza() { std::cout << "Vegan Deep Dish : " << T::AddIngredient(); } }; int main() { // unique_ptr is a smart pointer that disposes of // a pointer when it is no longer in use std::vector<std::unique_ptr<Pizza>> pizzaOrders; // Generate Pizza types and place them at the end of the vector pizzaOrders.emplace_back(new MeatNYStyle<LotsOfMeat<NYStyleCrust>>()); pizzaOrders.emplace_back(new VeganDeepDish<Vegan<DeepDishCrust>>()); // Call the pizzas and execute the directions // for making them for(auto &pizza: pizzaOrders){ pizza->MakePizza(); } return 0; } // ---------- END POLYMORPHIC TEMPLATES ---------- |
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