Re: Misuses of RTTI

OuFeRRaT wrote:
> "RTTI should only be used sparingly in C++ programs. There are several
> reasons for this. Most im****tantly, other language mechanisms such as
> polymorphism and templates are almost always superior to RTTI. As with
> everything, there are exceptions, but the usual rule concerning RTTI
> is more or less the same as with goto statements. Do not use it as a
> shortcut around proper, more robust design. Only use RTTI if you have
> a very good reason to do so and only use it if you know what you're
> doing." as cited in
http://en.wikibooks.org/wiki/C%2B%2B_Programming/RTTI
> 
> I don't understand the sentence:
> "but the usual rule concerning RTTI is more or less the same as with
> goto statements" can anyone explain it?
Personally I do not buy that analogy. RTTI can and should be used in
cases where you have an object of a polymorphic type without any
reasonable way of handling the actual type at compile time.

Historically C++ did not have RTTI and, IIRC Bjarne Stroustrup was
originally against having it. However it was introduced along with
dynamic_cast in response to the fact that developers (skilled ones) of a
good number of libraries were synthesising the functionality of RTTI
manually (having hierarchies in which every class had a member that
identified the class. That
a) Shows that the functionality was useful
b) Was fragile (easy for someone adding a class to the hierarchy to
forget to add the required member

It was at that point (around 1994) that RTTI was added.


> 
> Furthermore, can we talk about the missues of RTTI?

Yes, and I am sure that like quite a number of other specialist features
of C++ it is abused by those who do not understand the alternatives
(another example of this is exceptions)

> 

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