iterators incompatible?

[wennuan]

Why?

#include <iostream>
using namespace std;
#include <list>

class B
{
public:
	B(int _x)
	{
		x = _x;
	}
	int Get()
	{
		return x;
	}
private:
	int x;
};

class A
{
public:
	list<B*> GetB()
	{
		return lstB;
	}
	
	void AddB(B* _b)
	{
		lstB.push_back(_b);
	}

private:
	list<B*> lstB;
};

int main(void)
{
	B* b1 = new B(1);
	B* b2 = new B(2);
	B* b3 = new B(3);

	A* a1 = new A();
	a1->AddB(b1);
	a1->AddB(b2);
	a1->AddB(b3);

	for (list<B*>::iterator iter = a1->GetB().begin();
		iter != a1->GetB().end(); ++iter)
	{
		cout << (*iter)->Get() << endl;
	}

	return 0;
}

[MrHutch]

GetB returns a copy of the list. When you call it in your loop, the begin and end calls are on different lists, so an iterator makes no sense.

Can either take a copy of the list then iterator over that:

auto listInstance = a1->GetB();
. . . 
for (list<B*>::iterator iter = listInstance.begin(); iter != listInstance.end(); ++iter)

Or avoid the copy all together with a reference:

const list<B*>& GetB() const
. . .
for (list<B*>::const_iterator iter = a1->GetB().begin(); iter != a1->GetB().end(); ++iter)
{
   cout << (*iter)->Get() << endl;
}

[CptJY]

	list<B*> lst = a1->GetB();

	for (list<B*>::iterator iter = lst.begin(); iter != lst.end(); ++iter)

[wennuan]

Thanks MrHutch.