The simplest way to create a member function returning reference to object

Question

I created a member function that returning reference to object.

I can do it like:

class Foo {
  Foo &ref(){
    return *this;
  }
}

ref returning object by look up this pointer.

Is there any way else to return object without using this?

EXPLAIN the reason:

The reason I don't want to use this is: the pointer occupy 4B in stack whereas the reference share the same memory

I need some operator (`<<` for example) that returing object — DMaster, May 08 '15 at 06:40
Is there a particular reason why not? It's like saying you want to add two integers without using `+`. — Brian Bi, May 08 '15 at 06:47
I wonder why in c++ class, we have `this` as a pointer but have not anything else as a reference, and why `this` must be pointer — DMaster, May 08 '15 at 06:51
@DMaster Is your real question "why is `this` a pointer and not a reference"? — molbdnilo, May 08 '15 at 06:52
Without using this? No! Without using this in that particular function? Yes, but it makes things more complicated, so I see no reason to do it. — MikeMB, May 08 '15 at 06:53

score 1 · Accepted Answer · answered May 08 '15 at 07:10

1

It sounds like you don't like this and you don't want to dereference any pointers. How about:

class Foo {
  private:
    int dummy;
  public:
    Foo& ref() {
        return reinterpret_cast<Foo&>(dummy);
    }
};
static_assert(std::is_standard_layout<Foo>::value,
              "Foo must be standard-layout!");

Because Foo is a standard-layout class and dummy is its first non-static data member and there are no base classes, the address of dummy is the same as that of the containing Foo.

Needless to say, this is a very silly way to return a reference to an object and I can't see any possible justification for doing it this way. Not wanting to write return *this; is like wanting to add two integers without using +. It just makes no sense at all.

answered May 08 '15 at 07:10

Brian Bi

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anyway, thank you. The reason I don't want to use `this` is: the pointer occupy 4B in stack whereas the reference share the same memory – DMaster May 08 '15 at 07:38
2

@DMaster That's simply not right. The generated machine code will usually have to store the address of a reference somewhere like it stores a pointer's value. In some cases a reference can be optimized out, but the same is true for pointers. – Brian Bi May 08 '15 at 07:48
@DMaster You can find questions like that on this site, e.g., http://stackoverflow.com/questions/7058339/c-when-to-use-references-vs-pointers – Brian Bi May 08 '15 at 22:21

The simplest way to create a member function returning reference to object

1 Answers1