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POWhen to use references vs. pointers
 

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    <p>I understand the syntax and general semantics of pointers versus references, but how should I decide when it is more-or-less appropriate to use references or pointers in an API?</p> <p>Naturally some situations need one or the other (<code>operator++</code> needs a reference argument), but in general I'm finding I prefer to use pointers (and const pointers) as the syntax is clear that the variables are being passed destructively.</p> <p>E.g. in the following code:</p> <pre><code>void add_one(int&amp; n) { n += 1; } void add_one(int* const n) { *n += 1; } int main() { int a = 0; add_one(a); // Not clear that a may be modified add_one(&amp;a); // 'a' is clearly being passed destructively } </code></pre> <p>With the pointer, it's always (more) obvious what's going on, so for APIs and the like where clarity is a big concern are pointers not more appropriate than references? Does that mean references should only be used when necessary (e.g. <code>operator++</code>)? Are there any performance concerns with one or the other?</p> <p>EDIT (OUTDATED):</p> <p>Besides allowing NULL values and dealing with raw arrays, it seems the choice comes down to personal preference. I've accepted the answer below that references <a href="https://google.github.io/styleguide/cppguide.html#Reference_Arguments" rel="noreferrer">Google's C++ Style Guide</a>, as they present the view that "References can be confusing, as they have value syntax but pointer semantics.".</p> <p>Due to the additional work required to sanitise pointer arguments that should not be NULL (e.g. <code>add_one(0)</code> will call the pointer version and break during runtime), it makes sense from a maintainability perspective to use references where an object MUST be present, though it is a shame to lose the syntactic clarity.</p>
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    1. USPeter Mortensen
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    1. COIt's clear that it may be modified when it's a non-const reference. A const reference, on the other hand, clearly states it can't be modified. They look the same on calling, but most of the time intellisense (or something similar) will tell you what's up, and you can deduce from that. Otherwise, you could just document your API ;)
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    2. COIt seems like you've already made your decision about which one to use when. Personally, I prefer to pass in the object that I'm acting on, whether or not I'm modifying it. If a function takes a pointer, that tells me that it's acting on pointers, i.e. using them as iterators in an array.
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      1. USBenjamin Lindley
    3. CO@Schnommus: It's only clear when you're looking at the method declaration, it's not always convenient when reading over code to look at the definition of every method called.
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