[Development] New feature to qstring | QString::toBool()

jan-arve.saether at nokia.com jan-arve.saether at nokia.com
Wed Oct 26 08:31:37 CEST 2011

ext Thiago Macieira wrote on 2011-10-26:

> On Tuesday, 25 de October de 2011 23.33.04, Frans Klaver wrote:
>>> 1) document very well what is true and what isn't
>> Restricting the use to e.g. English only, would not be really useful 
>> when parsing (localized) user input, although I don't think this 
>> would happen a lot. I only know of a few cases where an end-user is 
>> expected to explicitly type yes or no into an input field, and those 
>> are command line tools. Wouldn't that be pretty much the only use case?
>> I might have overlooked things. It's getting late anyway.
> I agree with your argument, I just don't think it's applicable.
> QString is not localised and has never promised to be. QString::number 
> generates C-locale numbers and toInt/toDouble parse C-locale; 
> QDate::toString generates C-locale dates (or should), etc. If you want 
> localised information, you should use QLocale.
>>> 2) make sure all three classes work the same way. If not, change 
>>> them so that they all have toBool() const and they all operate equally.
>>> 3) add unit tests
>>> 4) ensure that QVariant::toBool calls into QString::toBool and 
>>> QByteArray::toBool, as applicable. Note pending the commits by 
>>> Jędrzej that are refactoring the QVariant internals.
>> If QString::toBool() is added, would there also be a need for 
>> something like static QString::boolean(bool value, char format = 't')?
> It's much easier to use the ternary operator and just select which 
> option you want to use.
I think the same argumentation (there is another, simple way) can be used for debating whether we should add QString::toBool().

I think I'm opposed to adding these functions, just because I don't see how they add value:

Consider this code:

bool parseOk;
if (str.toBool(&parseOk)) {
    if (parseOk)

then this:

if (str == QLatin1String("true")) {

which would you prefer?


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