QString fromStdString static function instead of constructor

Question

What is the reason for the choice of API below:

QString QString::fromStdString(const std::string & str) [static]

Why is there a need for calling a static function when we could have a constructor as follows:

QString::QString(const std::string & str)

There are similar constructors for the c string representation (char*), std::string being the exception. What is the reason for that?

I'd actually avoid QString(const char*) and use QLatin1String/QStringLiteral or QString::fromLatin1/QString::FromUtf8 etc. instead, for consciously and explicitly specifying the encoding used for conversion. — Frank Osterfeld
– Frank Osterfeld, Commented Apr 5, 2014 at 16:25
Noted! These calls also happen follow the static function pattern... — user1055604
– user1055604, Commented Apr 5, 2014 at 17:29
I believe this is the factory method pattern at work here... But I don't see they benefit of making an exception for coming strings? — user1055604
– user1055604, Commented Apr 5, 2014 at 17:35
An alternative could be having the constructor being explicit. — user2672165
– user2672165, Commented Apr 5, 2014 at 17:37

Massa · Accepted Answer · 2014-04-05 17:58:49Z

2

Qt predates explicit constructors, and it can't break its existing clients gratuitously. One other reason would be that std::string and QString are not necessarily in the same encoding/codepage and the static methods make explicit that some more expensive conversion is happening.

answered Apr 5, 2014 at 17:58

Massa

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