Reference vs. pointer

Question

What is the difference? Because this:

int Value = 50;
int *pValue = &Value;

*pValue = 88;

and ref version do the same:

int Value = 50;
int &rValue = Value;

rValue = 88;

Which one is better to use? Thanks.

Answer 1

In this case, they are equivalent.

It does not matter which you use, and neither is "best".

If you really want to choose between them then the reference is probably more idiomatic. I generally stick to references wherever I can because my OCD likes it: they feel "tighter", cannot be re-bound (with or without you noticing) and don't require a dereference to get to the value.

But I'm not aware of any general consensus on the issue for cases such as this.

Also note that the two may not compile to the same code if your implementation does not implement references with pointers, though I know of no implementation like that, and you wouldn't notice the difference anyway.

Answer 2

A pointer is the address of the memory location. You can change the value of that address to point at different memory addresses.

A reference is an alias of the variable. You can only assign this alias during declaration. You cannot change which variable the reference is an alias of after it's declared.

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The following pointer assignments are not possible with references.

int a = 10;
int b = 20;

int* pInt = NULL; // A pointer pointing at nothing.
pInt = &a; // pInt now points at a
pInt = &b; // pInt now points at b

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As for which one is better, it all depends on context.

I use references for method and function parameters.

void updateFoo(Foo& foo)

I use references to alias complex objects.

Foo& foo = bar.getBaz().getFoo(); // easy access to foo

I use pointers for dynamically allocated objects.

Foo* pFoo = new Foo();

I use pointers for things which may point at different values (including no value at all).

Foo* pFoo = NULL;

if (condition1)
    pFoo = &foo1;
else (condition2)
    pFoo = &foo2;

As a general rule, I default to references and use pointers in places where the limitations on references cause problems.