C ++受保护的/公共重载

class Foo
{
public:
    Foo()
    {
        for(int i = 0; i < 10; ++i)
            v.push_back(i);
    };
    const vector<double>& V() const {return v;};
protected:
    vector<double>& V() {return v;};
private:
    vector<double> v;
};

Foo foo;
for(int i = 0; i < (int) foo.V().size(); ++i)
    cout << foo.V().at(i) << endl;

V()

Foo foo;
const vector<double>& test = foo.V();
for(int i = 0; i < (int) test.size(); ++i)
    cout << test.at(i) << endl;

const vector<double>& test = const_cast<Foo const&>(foo).V();

ConstV

cbegin()

cend()

Foo foo;
Foo const& foo_alias = foo;
for (std::size_t i = 0; i != foo_alias.V().size(); ++i)
    cout << foo_alias.V().at(i) << endl;

foo

const

    Foo foo;
    const Foo& cFoo = foo;
    for(int i = 0; i < (int) cFoo.V().size(); ++i)
    cout << cFoo.V().at(i) << endl;

const

const

Foo foo;
const Foo& cfoo = foo; 

for(int i = 0; i < (int) cfoo.V().size(); ++i)
    cout << cfoo.V().at(i) << endl;