Iterate std::list<boost::variant>
How would you check for the object type when looping std::list?
class A
{
int x; int y;
public:
A() {x = 1; y = 2;}
};
class B
{
double x; double y;
public:
B() {x = 1; y = 2;}
};
class C
{
float x; float y;
public:
C()开发者_开发问答 {x = 1; y = 2;}
};
int main()
{
A a; B b; C c;
list <boost::variant<A, B, C>> l;
l.push_back(a);
l.push_back(b);
l.push_back(c);
list <boost::variant<A, B, C>>::iterator iter;
for (iter = l.begin(); iter != l.end(); iter++)
{
//check for the object type, output data to stream
}
}
From boost's own example:
void times_two( boost::variant< int, std::string > & operand )
{
if ( int* pi = boost::get<int>( &operand ) )
*pi *= 2;
else if ( std::string* pstr = boost::get<std::string>( &operand ) )
*pstr += *pstr;
}
i.e. Using get<T>
will return a T*
. If T*
is not nullptr
, then the variant is of type T
.
Same as how you determine the type from a regular variant.
for (iter = l.begin(); iter != l.end(); iter++)
{
//check for the object type, output data to stream
if (A* a = boost::get<A>(&*iter)) {
printf("%d, %d\n", a->x, a->y);
} else ...
}
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