Sams Teach Yourself C++ in 21 Days

Exploiting References 281

9

The counterargument is that the type is Cat. The &is part of the “declarator,” which

includes the variable name and the ampersand. More important, having the &near the

Catcan lead to the following bug:

Cat& rFrisky, rBoots;

Casual examination of this line would lead you to think that both rFriskyand rBoots

are references to Catobjects, but you’d be wrong. This really says that rFriskyis a ref-

erence to a Cat, and rBoots(despite its name) is not a reference but a plain old Catvari-

able. This should be rewritten as follows:

Cat &rFrisky, rBoots;

The answer to this objection is that declarations of references and variables should never

be combined like this. Here’s the right way to declare the reference and nonreference

variable:

Cat& rFrisky;

Cat boots;

Finally, many programmers opt out of the argument and go with the middle position, that

of putting the &in the middle of the two, as illustrated in case 2.

Of course, everything said so far about the reference operator (&) applies equally well to

the indirection operator (*). The important thing is to recognize that reasonable people

differ in their perceptions of the one true way. Choose a style that works for you, and be

consistent within any one program; clarity is, and remains, the goal.

Many programmers like the following conventions for declaring references

and pointers:

• Put the ampersand and asterisk in the middle, with a space on either
  side.


• Never declare references, pointers, and variables all on the same line.

NOTE

Returning Out-of-Scope Object References ........................................................

After C++ programmers learn to pass by reference, they have a tendency to go hog-wild.

It is possible, however, to overdo it. Remember that a reference is always an alias to

some other object. If you pass a reference into or out of a function, be certain to ask

yourself, “What is the object I’m aliasing, and will it still exist every time it’s used?”

Listing 9.13 illustrates the danger of returning a reference to an object that no longer

exists.