错误：没有匹配的 function 调用 'Node::Node()' - second(std::forward<_Args2>(std::get<_Indexes2>(__tuple2))...)

Question

I've defined a structure like this:

struct Node
{
   int32_t a;
   int32_t b;
   double c;
   double d;
 
   Node (int32_t a, int32_t b, double c)
   {
     this->a = a;
     this->b = b;
     this->c = c;
     this->d = 0.0;
   }
};

I'm implementing a map of map like this:

unordered_map<UInt32,unordered_map<int32_t,Node>> data;

Upon using the below code. I'm receiving error error: no matching function for call to 'Node::Node()' second(std::forward<_Args2>(std::get<_Indexes2>(__tuple2))...)

data[instId][id].d += (value);

Please help out why I'm receiving error. I've also tried using auto& tree = data[instId]; tree[id].d += (value); auto& tree = data[instId]; tree[id].d += (value);

(PS: Pseudo code is mentioned)

Answer 1

It is because that unordered_map<int32_t,Node> tries to call the constructor Node() with no argument, and because you defined the constructor with three argument, Node() is deleted. Consider adding Node()=default; inside the class definition.