Insertion in a map

Question

我有一张机票和行李的地图，每张机票必须是唯一的，并且必须对应地图上的一个位置，是否可以只更改行李（m_bagage->second）而不更改密钥？

std::unordered_map<Ticket, bagage> m_consigne;

Answer 1

You cannot change keys in a map, they are const . Moreover keys in maps are unique. To change the value of an existing entry, given the key you can do

std::unordered_map<Ticket, bagage> m_consigne;
// add some entries
bagage b;
Ticket t;
m_consigne[t] = b;