How to create a custom pointer in C++?

Custom pointers in C++ are a way to enhance the functionality of standard pointers. Creating a custom pointer includes: 1. Creating a pointer type inherited from std::unique_ptr; 2. Implementing the required functionality in the custom pointer. For example, improve code robustness by creating custom pointers to verify that pointers are null.

#Creation and use of custom pointers in C++

In C++, a pointer is a variable that can store the address of another variable. However, sometimes we want to use pointers in a more flexible and robust way, and this is when custom pointers come in handy.

Creating a custom pointer

Creating a custom pointer involves the following steps:

1. Create a pointer type that starts with std::unique_ptr Inheritance:

template<typename T>
class MyPtr: public std::unique_ptr<T> {
    // 添加自定义功能
};

2. Implement required extra functionality in custom pointers, such as smart release or verifying pointer state.

Practical case: Verify non-null pointer

The following example creates a custom pointer that verifies whether the pointer is null and throws an exception to improve the robustness of the code:

// 创建一个检查非空的自定义指针
template<typename T>
class NonNullPtr: public std::unique_ptr<T> {
public:
    NonNullPtr(T* ptr) : std::unique_ptr<T>(ptr) {
        if (ptr == nullptr) {
            throw std::invalid_argument("NonNullPtr: Pointer cannot be null");
        }
    }
    
    // 其他方法和函数...
};

// 使用：
int main() {
    // 创建一个非空的指针
    NonNullPtr<int> ptr(new int(5));
    
    // 访问指针指向的值
    int value = *ptr;
    
    // 尝试创建空指针会导致异常
    try {
        NonNullPtr<int> null_ptr(nullptr);
    } catch (std::invalid_argument& e) {
        std::cout << "Caught invalid argument: " << e.what() << std::endl;
    }
    
    return 0;
}

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