. , .
: Vector, :
class Vector{
public:
class Size{}; //
enum {max = 32000}; //
Vector (int n){ //
if (n<0 || n>max) throw Size();
...
}
...
};
Vector Size:
try{
Vector * = new Vector(i);
...
}
catch (Vector::Size){
... //
}
. , , , . , .
, :
,
, ,
.
, , . new , - .
. , , , .
, . , , .
: .
class Matherr{};
class Overflow: public Matherr{}; //
class Underflow: public Matherr{}; //
class ZeroDivide: public Matherr{}; //
/ :
class IOerr{};
class Readerr: public IOerr{}; //
class Writerr: public IOerr{}; //
class Seekerr: public IOerr{}; //
, , .
, C++. exception, <stdexcept>. , new bad_alloc.
|
|
|
, .
2.16
: ++
++ , , const_cast, dynamic_cast, reinterpret_cast static_cast.
const_cast const.
:
const_cast <> ();
, , const ( ).
, , . , const, .. . const , . const_cast , . , , , .
:
void print (int *p) { // *
cout << *;
}
const int *p;
print(p); // ,
void print (int *p) { // *
cout << *;
}
const int *p;
print(const_cast<int*>p); // ,
const_cast , , , , . , const, .
static_cast :
,
,
.
, static_cast .
:
static_cast <> ();
, , . , .
:
float f = 100;
int i = static_cast <int> (f); //
, , .
reinterpret_cast (, ), void* . , .
:
reinterpret_cast <> ();
, , .
:
char * = reinterpret_cast <char*>(malloc(100));
|
|
|
long l = reinterpret_cast <long>(p);
static_cast reinterpret_cast , , . static_cast, - reinterpret_cast.
dynamic_cast , - .
:
dynamic_cast < *> ();
, - .
- . , , , - , y, bad_cast.
(downcast), - (upcast) .. . , , (crosscast).
dynamic_cast :
class { / *... * / };
class : public { /*... */ };
* = new ;
* b = dynamic_cast<B*>(c); // * b = ;
dynamic_cast - .
, . , . RTTI (run-time type information) - . dynamic_cast , .. .
dynamic_cast , , .
, , , .. , , , , dynamic_cast .
dynamic_cast .
RTTI typeinfo.h .
:
, f2. dynamic_cast , f2 demo, , , .
#include <iostream.h>
#include <typeinfo.h>
class B{
...
public: virtual void f1 () {...};
};
class C: public B {
...
public: void f2() {cout << "f2";}
};
void demo (B* p) {
C* = dynamic_cast<C*>(p);
if (c) c->f2();
else cout << " ";
}
int main(){
* b = new ;
demo(b); // " "
|
|
|
* = new :
demo(c); // "f2" ()
return 0;
}
dynamic_cast :
* = (*) ;
. , .
- . dynamic_cast , .
: .
, :
#include <iostream.h>
#include <typeinfo.h>
class A{
...
public: virtual ~A(){... };
};
class B: public virtual A{... };
class C: public virtual A{... };
class D: public B, public C{... };
void demo(A *a) {
D* d = dynamic_cast<D*>(a);
if (d) {... }
}
int main(){
D *d = new D;
demo(d);
return 0;
}
- , . , dynamic_cast .
, bad_cast.
:
#include <iostream.h>
#include <typeinfo.h>
class B{
...
public: virtual void fl () {... };
};
class C: public B{
...
public: void f2(){... };
};
void demo (B& p) {
try{
C& = dynamic_cast<C&>(p);
c.f2();
}
catch (bad_cast) {
...
}
}
int main(){
B* b = new B;
demo(*b); //
* = new ;
demo(*c); //
return 0;
}
