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c++templatesambiguous-call
user2675345
user2675345

Reputation: 541

C++ template and ambiguous function call

Some code I have no control over has a number of overloaded functions which accepts different types

i.e.

setValue(int)
setValue(std::string)
setValue(bool)

And I have a template function which would idealy take any one of these types and pass it on to the correct setValue function.

template <class T>
do_something(T value) {
    ...
    setValue(value);

But I get this error 

error: call to member function 'SetValue' is ambiguous

Is there anything I can do to work around this problem without copy and pasting my code for each type like the writers of setValue have?

Upvotes: 3

Views: 3052

Answers (2)

Jarod42
Jarod42

Reputation: 218323

by defining you own SetValue with exact match and forwarding to the correct overload.

void setValue(int i) { setValue(static_cast<double>(i)) }

or (if you have a lot of "setValue" functions with same type) you may help the compiler to choose which overload to use like this:

void setValue(char a);
void setValue(double a);

template <typename T>
struct TypeToUseFor
{
    typedef T type;
};

template <>
struct TypeToUseFor<int>
{
    typedef double type;
};

template <class T>
void func(T value)
{
    setValue(static_cast<typename TypeToUseFor<T>::type>(value));
//    setValue(value);
}

int main() {
    func(0);   // int -> ?
    func('0'); // exact match
    func(0.0); // exect match
    func(0.f); // float -> double

    return 0;
}

Upvotes: 1

k06a
k06a

Reputation: 18825

I have no problems with:

void setValue(int a)
{
}

void setValue(std::string a)
{
}

void setValue(bool a)
{
}

template <class T>
void func(T value)
{
    setValue(value);
}

int main()
{
    func(5);
}

Here is my run: http://codepad.org/1wq8qd7l

Upvotes: 0

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