Regex return nothing with QRegularExpression

Drdgekil

hi everyone,

I have created a desktop application with QT 5.13.2 and MSVC 2017 32 bit
It's an electronic stock manager with mongoDB in background

I'm doing the search engine for my app.
I've a search Field, where i can use some basic syntax.

eg:

Search with value only:

value
value,value,value;
value|value|value;

Search with referenced value

ref=value
ref=value&ref=value&ref=value;
ref=value|ref=value|ref=value;

First i planned to implement a parser, but i thinks it's a bit oversized for this purpose. So i'm gonna using regex, but i never doing that before.

I have doing on regex101.com my regex that seem do be fonctional on the site, but when i run it with QRegularExpression they don't return the same thing.

They are in PCRE .

reference value = ([\w]{1,}[\s]{0,})([\=|\<|\>])([\s]{0,}[\w]{1,})([\s]{0,}[\&|\||\<|\>\;])
value only = ([\w]{1,}[\,\h\;\|\|]{1})

actually for the two regex, if i input :
value
OR
ref=value
I need to add an semi colon a the end of text. how i could rig of that ?

And if the string is :
element=value&element=value&element=value;

and in debugger, i watch the QStringList the only thing that comes in is: "element"

could you please help me for this regex problem ?

My c++ code is: (I'm testing only referenced value here)

   const QString regexByRef = "([\\w]{1,}[\\s]{0,})([\\=|\\<|\\>])([\\s]{0,}[\\w]{1,})([\\s]{0,}[\\&|\\||\\<|\\>\\;])";
   const QString regexByValue = "([\\w]{1,}[\\,\\h\\;\\|\\&]{1})";
   QRegularExpression re(regexByRef,QRegularExpression::CaseInsensitiveOption);
   re.setPatternOptions(QRegularExpression::MultilineOption);
   if(re.isValid())
   {
       QRegularExpressionMatchIterator it = re.globalMatch(input);
       QStringList words;
       while (it.hasNext()) {
           QRegularExpressionMatch match = it.next();
           QString word = match.captured(1);
           words << word;
       }

   }

VRonin

const QRegularExpression re(QStringLiteral(R"***((?:[\,\;\h\|]?(\w+))|(?:([\&\|\<\>]?)(\w+)\s*=\s*(\w+)\s*\;?))***"));
QRegularExpressionMatchIterator it = re.globalMatch(input);
while (it.hasNext()) {
const QRegularExpressionMatch match = it.next();
switch(match.lastCapturedIndex()){
case 1: //value only
qDebug() << "Captured Value: " << match.capturedRef(1);
break;
case 2: // first referenced value
qDebug() << match.capturedRef(1) << "=" << match.capturedRef(2);
break;
case 3: //subsequent referenced value
qDebug() << "Separator: " << match.capturedRef(1);
qDebug() << match.capturedRef(2) << "=" << match.capturedRef(3);
break;
default:
Q_UNREACHABLE();
break;
}
}

Drdgekil

Hi @VRonin
Thanks for your response,

i've tried your code.
if i input:

element=value&element=value&element=value;

it returns me :

element 
value

but i need the separator everytime, plus it gave me only the first occurence of

element=value

after that it raise the exception Q_UNREACHABLE

VRonin

ok, this is tested and should be working:

#include <QRegularExpression>
#include <QDebug>
int main(int argc, char *argv[])
{
    const QString inputs[] = {
        QStringLiteral("value")
        ,QStringLiteral("value,value,value;")
        ,QStringLiteral("value|value|value;")
        ,QStringLiteral("ref=value")
        ,QStringLiteral("ref=value&ref=value&ref=value;")
        ,QStringLiteral("ref=value|ref=value|ref=value;")
        ,QStringLiteral("element=value&element=value&element=value;")
    };
    const QRegularExpression re(QStringLiteral(R"***(([\&\|\<\>\h,]?)(\w+)\s*(?:=\s*(\w+)\s*\;?)?)***"));
    for(const QString& input : inputs){
        qDebug() << "Input: " << input;
        QRegularExpressionMatchIterator it = re.globalMatch(input);
        while (it.hasNext()) {
            const QRegularExpressionMatch match = it.next();
            switch(match.lastCapturedIndex()){
            case 2:
                qDebug() << "Value Only";
                if(!match.capturedRef(1).isEmpty())
                    qDebug() << "Previous separator: " <<  match.capturedRef(1);
                qDebug() << "Value: " <<  match.capturedRef(2);
                break;
            case 3:
                qDebug() << "Referenced Value";
                if(!match.capturedRef(1).isEmpty())
                    qDebug() << "Previous separator: " <<  match.capturedRef(1);
                qDebug() << "Value: " <<  match.capturedRef(2) << "=" << match.capturedRef(3);
                break;
            default:
                Q_UNREACHABLE();
                break;
            }
        }
    }
    return 0;
}

Drdgekil

Hi,
thanks it's working like a charm.

what is the utility of the R"*** ?

VRonin

@Drdgekil said in Regex return nothing with QRegularExpression:

what is the utility of the R"*** ?

It's a raw string literal, it allows you not to care about escaping characters in the string

Drdgekil

thanks for your help, it's very appreciate