Getting std::string object from QString object ( qt3)

[Yes]

QString qstr = "xxx";
std::string str = qstr;

QString qstr = "xxx";
std::string str = qstr;

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This should work fine.

If not, you can do:

QString qstr = "xxx";
std::string str(qstr.ascii());

QString qstr = "xxx";
std::string str(qstr.ascii());

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When I try

QString qstr = "xxx";
std::string str = qstr;

QString qstr = "xxx";
std::string str = qstr;

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it works fine. But when I try

QString qstr = "xxx";
std::string str;
str = qstr;

QString qstr = "xxx";
std::string str;
str = qstr;

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I get error: ambiguous overload for 'operator=' in 'str = qstr'. Why is that? Is conversion between QString and std::string well defined while assignment of a QString on an already created std::string becomes ambiguous?