data member 'vec' cannot be a member template
I have the following two lines in a header in order to declare a vector containing a template:
template <class t>
std::vector <t> vec;
However I get the following error: data member 'vec' cannot be a member template What did I do wrong? Edit: I don't know that I was understood correctly, I am trying to declare a vector which contains a template, I know that this can be done as one can have the following:
template <class T>
void funct(vector <T> v){
}
this function takes a vector of a template as it's parameter, I wish to do the same thing except with declaring the vector in a header in order to allow the vector to contain anything.
The template <> statement is only used when declaring a function template or a class template. For example you can use it when you declare (and define) a class:
template <typename T>
class TemplateClass {
/* definition */
};
Or a function:
template <typename T>
void templateFunc(T value) {
/* definition */
}
When creating an instance of the class, you can't use the template <> statement. Instead you specify a template parameter like this:
TemplateClass<int> tc;
And when calling a template function:
int i = 1;
templateFunc(i); // <-- Automatic template deduction to int.
Such vector can't contain anything. Let's suppose that a compiler let you declare such a vector, and you write a code like
//...
A Aobj;
vec.push_back(Aobj);
//...
Then size of one element in the vec will be the sizeof(A) . But next you writes
//...
B Bobj;
vec.push_back(Bobj);
//...
What the size of one element here should be?
Anyway, as a workaround you may declare vector<void*> vec this going to contain a pointers to anything you wanted.
Vector always need a class T as template. But the template should be put ahead of class declaration.
You probably mean
template<class T>
class A {
private:
std::vector<T> vec;
};
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