How to write a constexpr function returning a QString?

Question

I try to write function with constexpr

constexpr QString c(const QString &columnName);

but it output issue:

enclosing class of constexpr non-static member function 'QString DatabaseHandler::c(const QString&) const' is not a literal type constexpr QString c(const QString &columnName);

I very bad know C++ 11 yet so cannot undestand this bug. What does it mean?
P.S. If I add static then it also output issue Invalid return type 'QString'.

Dimitrios Bouzas · Accepted Answer · 2015-12-21 21:56:18Z

7

constexpr functions require that their input arguments and their return type are literal types, and therefore must have at least one constexpr constructor. Qstring (i.e, the return type) does not, thus you get a compiler error.

edited Dec 21, 2015 at 21:56

answered Dec 21, 2015 at 21:46

Dimitrios Bouzas

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4 Comments

Denis Steinman Over a year ago

I didn't know... Thanks! I read now that Qt 4.8 supports C++ 11, so I think that it must have this constructor. Or I don't understand something?

Piotr Skotnicki Over a year ago

A reference type is a literal type. In the OP's case, it's the return type that is not of a literal type, isn't it?

Denis Steinman Over a year ago

I found now QStringLiteral define but I cannot understand how to use it

Dimitrios Bouzas Over a year ago

@PiotrSkotnicki Yeah, I corrected thanx, you rock ;)

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