[英]Call function of objects in a Variadic Template
I have a template object that can hold different data types, and a method called get()
. 我有一个可以容纳不同数据类型的模板对象,还有一个名为get()
的方法。 get()
returns the value of the data type cast to an int
. get()
返回转换为int
的数据类型的值。
template <class T>
class A
{
public:
int get()
{
return (int) m_val;
}
void set(T t)
{
m_val = t;
}
private:
T m_val;
};
I also have a variadic template function that would take in multiple objects of A, and call their get()
methods, adding together the values and returning the result. 我还有一个可变参数的模板函数,该函数可以接受A的多个对象,并调用它们的get()
方法,将值加在一起并返回结果。 However, I am fairly new to variadic templates and have no idea what I am doing. 但是,我对可变参数模板还很陌生,也不知道我在做什么。 This is what I've got, after looking around at them: 这是我环顾四周后得到的:
//Ensure only types of A can be used for getStuff
template <>
int getStuff<A>(A... t)
{
int val = 0;
val = val + (t...).get();
}
int main() {
A<int> a;
A<char> b;
a.set(5);
b.set(100);
int val = getStuff(a, b);
printf("%d", val);
return 0;
}
Obviously, this does not compile. 显然,这不能编译。 What am I doing wrong? 我究竟做错了什么? Do I need to get a pointer to each of the different A's and iterate over them? 我是否需要获得指向每个不同A的指针并对其进行迭代?
prog.cpp:23:13: error: expected initializer before '<' token
int getStuff<A>(A... t)
^
prog.cpp: In function 'int main()':
prog.cpp:37:25: error: 'getStuff' was not declared in this scope
int val = getStuff(a, b);
You're close ! 你近了! Here is a non-recursive way, perfect-forwarding included free of charge : 这是一种非递归的方式,免费包含完善的转发功能:
template <class... As>
int getStuff(As&&... as)
{
int val = 0;
for(int i : {std::forward<As>(as).get()...})
val += i;
return val;
}
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