是否有可能接受两种不同类型的lambda函数作为类成员而不知道他们的模板参数提前？
struct two_functors {
std::function<???> a;
std::function<???> b;
...
};
这样的事情是可能的：
void main(){
vector<two_functors> many_functors;
int a = 2;
int b = 3;
double c = 4.7;
double d = 8.4;
two_functors add_and_subtract;
add_and_subtract.a = [a,b](int x,int y){cout << x + y << endl;};
add_and_subtract.b = [c,d](double x,double y){cout << x - y << endl;};
two_functors multiply_and_divide;
multiply_and_divide.a = [c,double y){cout << x * y << endl;};
multiply_and_divide.b = [a,int y){cout << x / y << endl;};
many_functors.push_back(add_and_subtract);
many_functors.push_back(multiply_and_divide);
for (auto functors : many_functors){
functors.a();
functors.b();
}
}
解决方法
如果您只想在不同时间构造two_functors,但是稍后按顺序执行它们,您可以只使用捕获的数据.
struct two_functors
{
function<void ()> a;
function<void ()> b;
};
int main()
{
vector<two_functors> many_functors;
int a = 2;
int b = 3;
double c = 4.7;
double d = 8.4;
two_functors add_and_subtract {
[a,b](){cout << a + b << endl;},[c,d](){cout << c - d << endl;}
};
two_functors multiply_and_divide {
[c,d](){cout << c * d << endl;},[a,b](){cout << a / b << endl;}
};
many_functors.push_back(add_and_subtract);
many_functors.push_back(multiply_and_divide);
for (auto functors : many_functors){
functors.a();
functors.b();
}
}