Qt - How to get a string between 2 character?

Question

I am working on Qt using string. How can I get a string between 2 characters are '#' and ':'

my strings below:

#id:131615165

#1:aaa,s1

#23:dd

#526:FE

the result that I want to get is: "id", "1", "23", "526".

Many thanks for any help.

There's a saying going something like this: A programmer had a problem. He decided to solve it using regular expressions. Now the programmer have two problems. A regular expressions is a powerful tool in the right situation, but also very complex and prone to introducing bugs. In your case, you could simply find the position of the ':', then get the sub-string up to that position, and skip the first character (the '#'). It's simple and easy to write and debug. — Some programmer dude
– Some programmer dude, Commented Apr 3, 2019 at 8:52

Dimitry Ernot · Accepted Answer · 2019-04-03 09:07:22Z

3

QString based solution:

QString s("    #iddfg:131615165");
int startPos = s.indexOf('#') + 1;
int endPos = s.indexOf(':');
int length = endPos - startPos;
qDebug() << startPos << length << s.mid(startPos, length);

answered Apr 3, 2019 at 9:07

Dimitry Ernot

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Comments

kefir500 · Accepted Answer · 2019-04-03 09:45:08Z

3

Solution using `QRegularExpression`:

QRegularExpression regex("^#(.+?):");
qDebug() << regex.match("#id:131615165").captured(1);

Pattern explanation:

^ matches the start of a line
# matches the # character
(.+?) is a capture group where:
- . matches any character except line terminators
- + matches one or more characters
- ? is a "lazy" match to handle situations where multiple colons are present in the string.
: matches the : character

edited Apr 3, 2019 at 9:45

answered Apr 3, 2019 at 9:30

kefir500

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1 Comment

ΦXocę 웃 Пepeúpa ツ Over a year ago

why are you posting twice?... please, next time consider editing the answer instead of re posting the same answer....

Amfasis · Accepted Answer · 2019-04-03 10:00:18Z

2

I highly recommend an online regex-tester to start with the regex, for example: https://regex101.com

Using the following code you can capture the data from a QString:

QString input = "#id:131615165";
QRegExp test("#(.*):");
if(test.exactMatch(input))
{
    qDebug() << "result:" << test.cap(1);
}

edited Apr 3, 2019 at 10:00

answered Apr 3, 2019 at 8:53

Amfasis

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2 Comments

Chinh Nguyen Huu Over a year ago

I tried it, a warning is unknown escape sequence '\#' appear

Amfasis Over a year ago

Sorry my bad, post has been edited by removing the extra slash (was copied wrongly from regex101.com)

Martin Hennings · Accepted Answer · 2019-04-03 09:27:04Z

0

As @Someprogrammerdude wrote in the comments:

QString getTag(QString const &input)
{
    QString result;
    int idx = input.indexOf(':');
    if(input.startsWith('#') && idx > 1) {
        int len = idx - 1;
        result = input.mid(1, len); // [0]='#', [idx]=':'
    }
    return result;
}

answered Apr 3, 2019 at 9:27

Martin Hennings

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