Iterating over a QMap with for

Question

I\'ve a QMap object and I am trying to write its content to a file.

QMap extensions;
//.. 

for(auto e : extensions)
{
  fou         


        

Answer 1

QMap::iterator uses key() and value() - which can be found easily in the documentation for Qt 4.8 or the documentation for Qt-5.

Edit:

A range-based for loop generates codes similar to this (see CPP reference):

{
    for (auto __begin = extensions.begin(), __end = extensions.end();
            __begin != __end; ++__begin) {
        auto e = *__begin; // <--- this is QMap::iterator::operator*()
        fout << e.first << "," << e.second << '\n';
    }
} 

QMap::iterator::iterator*() is equivalent to QMap::iterator::value(), and does not give a pair.

The best way to write this is without range-based for loop:

auto end = extensions.cend();
for (auto it = extensions.cbegin(); it != end; ++it)
{
    std::cout << qPrintable(it.key()) << "," << qPrintable(it.value());
}