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POShould I use #define, enum or const?
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  1. POShould I use #define, enum or const?
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    copied!<p>In a C++ project I'm working on, I have a <em>flag</em> kind of value which can have four values. Those four flags can be combined. Flags describe the records in database and can be:</p> <ul> <li>new record</li> <li>deleted record</li> <li>modified record</li> <li>existing record</li> </ul> <p>Now, for each record I wish to keep this attribute, so I could use an enum:</p> <pre><code>enum { xNew, xDeleted, xModified, xExisting } </code></pre> <p>However, in other places in code, I need to select which records are to be visible to the user, so I'd like to be able to pass that as a single parameter, like: </p> <pre><code>showRecords(xNew | xDeleted); </code></pre> <p>So, it seems I have three possible appoaches:</p> <pre><code>#define X_NEW 0x01 #define X_DELETED 0x02 #define X_MODIFIED 0x04 #define X_EXISTING 0x08 </code></pre> <p>or</p> <pre><code>typedef enum { xNew = 1, xDeleted, xModified = 4, xExisting = 8 } RecordType; </code></pre> <p>or </p> <pre><code>namespace RecordType { static const uint8 xNew = 1; static const uint8 xDeleted = 2; static const uint8 xModified = 4; static const uint8 xExisting = 8; } </code></pre> <p>Space requirements are important (byte vs int) but not crucial. With defines I lose type safety, and with <code>enum</code> I lose some space (integers) and probably have to cast when I want to do a bitwise operation. With <code>const</code> I think I also lose type safety since a random <code>uint8</code> could get in by mistake.</p> <p>Is there some other cleaner way?</p> <p>If not, what would you use and why?</p> <p>P.S. The rest of the code is rather clean modern C++ without <code>#define</code>s, and I have used namespaces and templates in few spaces, so those aren't out of question either.</p>
 

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