问题
I couldn't find a way to set a custom comparator function for QMap, like I can for std::map (the typename _Compare = std::less<_Key> part of its template arguments).
Does QMap have a way to set one?
回答1:
It's not documented (and it's a mistake, I think), but in you can specialize the qMapLessThanKey template function for your types (cf. the source). That will allow your type to use some other function rather than operator<:
template<> bool qMapLessThanKey<int>(const int &key1, const int &key2)
{
return key1 > key2; // sort by operator> !
}
Nonetheless, std::map has the advantage that you can specify a different comparator per each map, while here you can't (all maps using your type must see that specialization, or everything will fall apart).
回答2:
No, as far as i know QMap doesn't have that functionality it requires that it's key type to have operator<, so you are stuck with std::map if you really need that compare functionality.
回答3:
QMap's key type must provide operator<(). QMap uses it to keep its items sorted, and assumes that two keys x and y are equal if neither x < y nor y < x is true.
In case, overload operator<().
来源：https://stackoverflow.com/questions/17463889/does-qmap-support-custom-comparator-functions