FAQ-0825 Is TBufC immutable?


FAQ-0825 Is TBufC immutable?

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Classification:	C++	Category:	Base
Created:	09/20/2002	Modified:	12/06/2002
Number:	FAQ-0825
Platform:	Not Applicable

Question:
TBufC is described as a non-modifiable buffer descriptor. Since its buffer is private, its Ptr() method returns a const pointer and it has no methods which allow its data to be modified after initialisation, is it safe to assume that the data of a TBufC is immutable?

Answer:
No it is not. TBufC has a Des() method (as does HBufC) which returns a TPtr, so allowing any (so-called) non-modifiable buffer descriptor to be exchanged for a modifiable one. The "C" really indicates no more than an intention about how the descriptor should be used.

So if you find yourself using the Des() function, you should probably ask yourself:

if it's for a TBufC declared in your own code, should you not rather have declared a TBuf?
if it's for a descriptor declared in another class, are you conforming to the intention of the designer of that class for this descriptor's data not to be modified?