17 REFERENCES in C++

1. Relationship with Pointers

In fact, a reference is just an extension of a pointer, a kind of syntax sugar based on pointers, designed to make code easier to read and write. As the name suggests, a reference is a way to refer to an existing variable. There is nothing that a reference can do that a pointer cannot.

Unlike pointers (where you first create a pointer variable and then assign it nullptr, etc.), a reference must refer to an existing variable. The reference itself is not a new variable and does not actually occupy memory.

2. Defining References

This is achieved through type&, where the & is part of the type. Therefore, the presence of & does not necessarily mean taking an address or being a reference; it depends on the context.

In any case, ref is a. We are simply creating an alias for a to make the code easier to write.

3. Example

void Increment(int value)
{
    // int value = 5;
    value++;
}

int main()
{
    int a =5;
    Increment(a);
    LOG(a); // 5
}

Here, we are using passing by value, not int& or int*. Therefore, a new variable is copied with the value 5, and a is not changed.

What we need is passing by reference to increment the variable.

As shown in the image above, first dereference, then increment the value at that address. However, this looks cumbersome, so we can use the following approach:

Using References

The code is clearer and more concise, enhancing readability.

4. Other Notes

Once you declare a reference, you cannot change the object it refers to.

int a = 5;
int b = 8;

int& ref = a;
ref = b;  // a=8,b=8

Additionally, once declared, it must be immediately assigned because it is a reference to a variable, not an actual variable.

If you want to modify the reference, you can do so through pointers (pointers can change the object they point to, while references cannot).