Usage of const pointers and immutable objects in C++

In C++, const pointers point to data that cannot be modified, while immutable objects have the characteristics that they cannot be modified. The main advantages: const pointers: prevent the data pointed to from being accidentally written and ensure data integrity. Immutable objects: By making class member variables const, objects that cannot be modified are created to ensure data security.

Usage of const pointers and immutable objects in C++

In C++, pointers and immutable objects manage data memory and prevent accidental writing Two powerful tools. Knowing how to use them correctly is crucial to writing robust, error-free code.

const pointer

const pointer is a pointer to a constant value or object. This means that the data accessed through this pointer cannot be modified. Declare a const pointer like this:

const int* pointer_to_const_int;  // 指向常量 int 的指针

One of the main advantages of const pointers is protection against accidental writes. For example, consider the following code:

int value = 10;
int* pointer_to_value = &value;  // 非 const 指针

*pointer_to_value = 20;  // 修改 value 的值

In the above example, pointer_to_value is a non-const pointer, allowing us to change the value pointed to. If we try to do this, the compiler will issue an error:

const int* pointer_to_const_int = &value;  // const 指针

*pointer_to_const_int = 20;  // 错误：试图修改 const 值

Immutable objects

Immutable objects are objects that cannot be modified. In C++, immutable objects are typically created by declaring class members as const:

class MyClass {
public:
    const int value;  // const 成员变量

    MyClass(const int& value) : value(value) {}
};

After creating a MyClass object and assigning a value to its members, the value Cannot be modified. We can use pointers to immutable objects just like const pointers:

MyClass object(10);
const MyClass* pointer_to_const_object = &object;

pointer_to_const_object->value;  // 访问 const 成员变量

Practical case

The following are examples of the use of const pointers and immutable objects in actual projects:

String constants in C++

String constants in C++ are actually examples of immutable objects. We can use const pointers to these strings, like this:

const char* message = "Hello World!";

This way, we can safely use the string without worrying about accidentally modifying its content.

Protect sensitive data

We can use const pointers and immutable objects to protect sensitive data, such as passwords or financial information. By storing data in immutable objects and accessing them using const pointers, we prevent unauthorized changes.

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