How to set value in c unordered_map and return reference?-CodePudding

So this is silly:

Nodes[pos] = node;
return &Nodes[pos];

because I insert and then do a lookup. I tried like this:

return &Nodes.emplace(pos, node).first->second;

but it doesn't return the reference.

CodePudding user response：

You can use insert/emplace like this:


int& f1(std::unordered_map<int, int>& m) {
  auto [iterator, was_inserted] = m.insert({10, 100});
  return iterator->second;
}

operator[] can also create the key if it doesn't exist, so you can also do:

int& f2(std::unordered_map<int, int>& m) {
  auto& node = m[10];
  node = 100;
  return node;
}