Cpp: Difference between revisions
No edit summary |
No edit summary |
||
| Line 6: | Line 6: | ||
Her er en udemærket artikel omkring [http://www.informit.com/articles/article.asp?p=461634&seqNum=3&rl=1 exception handling] | Her er en udemærket artikel omkring [http://www.informit.com/articles/article.asp?p=461634&seqNum=3&rl=1 exception handling] | ||
==C++ casting operators== | |||
(Citat fra Learning DCOM af Thuan L. Thai) | |||
We all know the power or evilness of the C-style cast, which allows us to cast a given type | |||
to practically any other type that we want. | |||
For example, we can cast a human into an ant. This can be extremely dangerous, because it | |||
can create uncontrollable and error-prone software. To migitate casting problems, C++ allows us to spcifically indicate the kind of cast that we want to apply. Check with compiler documentation for the details of the C++ casting operators. In a nutshell, here they are and their short meanings. | |||
*<code>dynamic_cast</code> | |||
**Used to convert polymorphic types. Runtime checks will be made to ensure the validity of the cast. If the cast is not safe, a <code>bad_cast</code> exception will be thrown. | |||
*<code>static_cast</code> | |||
**Used to convert nonpolymorphic types. No runtime check is involved. | |||
*<code>const_cast</code> | |||
**Used to cast away const-ness or volatile-ness of an object. | |||
*<code>reinterpret_cast</code> | |||
**Used to cast any pointer or integral type into another pointer or integral type. This is the most flexible and the most dangerous of the C++ casting operators, second only to the traditional C casting operator. | |||
In the old days, we would do the following to cast a double pointer into a void**: | |||
<code> | |||
(void**)(&pSome) | |||
</code> | |||
If we wanted to use the C++ casting operators, we would write the above code as follows: | |||
<code> | |||
reinteroret_cast<void**>(%pSome) | |||
</code> | |||
The syntax of the other C++ casting operators follows the same pattern as reinterpret_cast. | |||
Revision as of 11:05, 18 June 2006
Der er mange gode artikler om c++ på informit.com
Hvis at du har brug for noget generic funktionality som måske ikke lige ligger i STL er det værd at tage et kig på boost som er en samling af open/ source (licens a la BSD) general purpose klasser/libaries
Hvis at man vil have en lidt enklere tilgang til hukommelses styringen kan man bruge lidt tid på at undersøge RAII og brugen af f.eks. std::auto_ptr. Se evt også denne ONLamp artikel
Her er en udemærket artikel omkring exception handling
C++ casting operators
(Citat fra Learning DCOM af Thuan L. Thai)
We all know the power or evilness of the C-style cast, which allows us to cast a given type to practically any other type that we want. For example, we can cast a human into an ant. This can be extremely dangerous, because it can create uncontrollable and error-prone software. To migitate casting problems, C++ allows us to spcifically indicate the kind of cast that we want to apply. Check with compiler documentation for the details of the C++ casting operators. In a nutshell, here they are and their short meanings.
dynamic_cast- Used to convert polymorphic types. Runtime checks will be made to ensure the validity of the cast. If the cast is not safe, a
bad_castexception will be thrown.
- Used to convert polymorphic types. Runtime checks will be made to ensure the validity of the cast. If the cast is not safe, a
static_cast- Used to convert nonpolymorphic types. No runtime check is involved.
const_cast- Used to cast away const-ness or volatile-ness of an object.
reinterpret_cast- Used to cast any pointer or integral type into another pointer or integral type. This is the most flexible and the most dangerous of the C++ casting operators, second only to the traditional C casting operator.
In the old days, we would do the following to cast a double pointer into a void**:
(void**)(&pSome)
If we wanted to use the C++ casting operators, we would write the above code as follows:
reinteroret_cast<void**>(%pSome)
The syntax of the other C++ casting operators follows the same pattern as reinterpret_cast.