Overloaded function template never called
I love templates, at least I would if I would understand them ;-). I implemented an overloaded operator using templates. I am now trying to specialise the function calls.
Here is what I do:
class Terminallog {
public:
Terminallog();
Terminallog(int);
virtual ~Terminallog();
template <class T>
Terminallog & operator<<(const T &v);
template <class T>
Terminallog & operator<<(const std::vector<T> &v);
template <class T>
Terminallog & operator<<(const std::vector<T> *v);
template <class T, size_t n>
Terminallog & operator<<(const T(&v)[n]);
Terminallog & operator<<(std::ostream&(*f)(std::ostream&));
Terminallog & operator<<(const char v[]);
//stripped code
};
//stripped code
template <class T>
Terminallog &Terminallog::operator<<(const T &v) {
if (this->lineendet == true) {
this->indent();
}
this->lineendet = false;
std::cout << v;
return *this;
}
template <class T>
Terminallog &Terminallog::operator<<(const std::vector<T> &v) {
for (unsigned int i = 0; i < v.size(); i++) {
std::cout << std::endl;
this->indent();
std::cout << i << ": " << v.at(i);
}
std::cout << std::flush;
return *this;
}
template <class T>
Terminallog &Terminallog::operator<<(const std::vector<T> *v) {
for (unsigned int i = 0; i < v->size(); i++) {
std::cout << std::endl;
this->indent();
std::cout << i << ": " << v->at(i);
}
std::cout << std::flush;
return *this;
}
template <class T, size_t n>
Terminallog &Terminallog::operator<<(const T(&v)[n]) {
unsigned int elements = sizeof (v) / sizeof (v[0]);
for (unsigned int i = 0; i < elements; i++) {
std::cout << std::endl;
this->indent();
std::cout << i << ": " << v[i];
}
std::cout << std::flush;
return *this;
}
inline
Terminallog &Terminallog::operator<<(std::ostream&(*f)(std::ostream&)) {
if (f == static_cast<std::ostream & (*)(std::ostream&)> (std::endl)) {
this->lineendet = true;
}
std::cout << f;
return *this;
}
inline
Terminallog &Terminallog::operator<<(const char v[]) {
if (this->lineendet == true) {
std::cout << std::endl;
this->indent();
std::cout << v;
}
this->lineendet = false;
std::cout << v;
return *this;
}
//sripped code
Now I am trying something like
vector<int> *test3 = new vector<int>;
test3-开发者_如何转开发>push_back(1);
test3->push_back(2);
test3->push_back(3);
test3->push_back(4);
Terminallog clog(3);
clog << test3;
which compiles just fine. However executing the code, it prints the address of test3, instead all the elements. I conclude that the compiler thinks, that
Terminallog & operator<<(const T &v);
is a better match. However I don't know what to do about it. Where is the mistake in my code? Why is
Terminallog & operator<<(const std::vector<T> *v);
never called?
The type of test3
in your code is std::vector<int> *
, but there is no Terminallog::operator<<
that takes an argument of that type. There is one that takes const std::vector<int> *
and it would be called if you did
clog << const_cast<const vector<int>*>(test3);
Incidentally, new'ing a vector is almost never a good idea.
For it to match the pointer-to-const-vector version, a const needs to be added to the type and this is not a top-level const (const-pointer-to-vector, i.e std::vector<T>* const
). The chosen overload does not require any type conversions and is a better match.
I'd suggest completely removing the pointer overload, especially seeing that it just duplicates the vector reference overload. Instead just dereference the pointer.
clog << *test3;
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