no match for operator= using a std::vector
I've got a class declared like this:
class Level
{
private:
std::vector<mapObject::MapObject> features;
(...)
};
and in one of its member functions I try to iterate through that vector like this:
vector<mapObject::MapObject::iterator it;
for(it=features.begin(); it<features.end(); it++)
{
/* loop code */
}
This seems straightforward to me, but g++ gives me this error:
src/Level.cpp:402: error: no match for 开发者_开发知识库‘operator=’ in ‘it = ((const yarl::level::Level*)this)->yarl::level::Level::features.std::vector<_Tp, _Alloc>::begin [with _Tp = yarl::mapObject::MapObject, _Alloc =
std::allocator<yarl::mapObject::MapObject>]()’
/usr/include/c++/4.4/bits/stl_iterator.h:669: note: candidates are: __gnu_cxx::__normal_iterator<yarl::mapObject::MapObject*,
std::vector > >& __gnu_cxx::__normal_iterator<yarl::mapObject::MapObject*,
std::vector > >::operator=(const __gnu_cxx::__normal_iterator<yarl::mapObject::MapObject*, ``std::vector<yarl::mapObject::MapObject, std::allocator<yarl::mapObject::MapObject> > >&)
Anyone know why this is happening?
I'd guess that this part of the error describes your problem:
(const yarl::level::Level*)this
Is the member function in which this code is found a const-qualified member function? If so, you'll need to use a const_iterator
:
vector<mapObject::MapObject>::const_iterator it;
If the member function is const-qualified, then only the const-qualified overloads of begin()
and end()
on the member vector will be available, and both of those return const_iterator
s.
Did you close your right-angle bracket here?
vector<mapObject::MapObject::iterator it;
If you want a vector of objects, your object needs an operator=. Does MapObject have one? If not, consider a vector of pointers to MapObject.
If I were you, I would check to see that the mapObject::MapObject has a default constructor and a public assignment operator.
Somewhere in the class header, you should see something like:
public:
MapObject();
operator=(const MapObject &mapObject);
Which means that the class has a default constructor and an assignment operator.
A std::vector cannot be instantiated using a class without a default constructor, and you cannot iterate through the class as above without an assignment operator.
So, add an assignment operator to your class definition and your iteration will compile.
@James McNellis's answer (the "green checked" best answer) fixed my error with a similar description, however my error was caused by what @tmarthal mentioned his answer post (not defining an assignment operator). His suggested fix is to include an assignment operator but I just wanted to add that I was also able fix this error by using std::vector<>::const_iterator instead of std::vector<>::iterator for classes where no assignment operator is defined. I'm not sure whether this truly a correct fix or just something that kept the compiler from complaining however.
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