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Shouldn't TPtr have a default constructor if it encapsulate a pointer?
| Thu, 2005-08-25 18:09 | |
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I was wondering... Why isn't there a default constructor for TPtr? What if you wanted to do something like this: Code: void method(TPtr& aPtr) { aPtr = _L("blob") ; } TPtr ptr ; method(ptr) ; // now ptr points to "blob" The only I can see of doing something similar is like this: Code: void method(HBufC*& aBuf) { aBuf = HBufC16::NewL(4) ; aBuf->Des() = _L("blob") ; } HBufC* buf ; method(buf) ; // now buf points to "blob" Anyone has any better ideas of how do this? Anyone has a good explanation of why TPtr has no default contructor? Cheers, Nikolas. If we fall down it's so we can learn to pick ourselves up. |
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Forum posts: 121
Consider TPtrC, it does have a default constructor, however this class only allows you to read data. TPtrC's default constructor set's it's self to NULL, and length 0. So since your only use of a TPtrC will be read data, if you attempted to read some information from a TPtrC you'd end up with a descriptor of NULL content and zero length. - This makes sense.
Now consider TPtr, it's mean to be used for looking at, and modifying data... if it had a default constructor what would it set it's self too ? NULL and 0 length ? - Ok, but now what happens when you try to write to this descriptor.... you'd get a memory exception, and your app would panic and die - probably with an unhandled exception.
To prevent this, TPtr does not have a default constructor, so you have to set it to something before you can use it.