How to get a QString from a file (use regular expression)

[fengtian.we]

My case:
I hava a file: a.txt

a e-mail address is in the file.

how can i get the e-mail String??

[jpn]

QFile, QTextStream

[fengtian.we]

Now , I find a: bool QString::contains(const QRegExp & rx ) const

but it is return a bool value~ I need QStrings

[marcel]

But with the classes Jpn suggested you can read QStrings from a file.
Read the docs to find out how you can do that.

Regards

[fengtian.we]

no Class QString is not supply any method to get it.

[marcel]

Are you sure?
What about this:

QFile file("somefile.txt");
if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
   return;
QTextStream textStream( &file);
QString fileContents = textStream.readAll();

QFile file("somefile.txt");
if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
   return;
QTextStream textStream( &file);
QString fileContents = textStream.readAll();

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You can also read the stream in chunks, if the file is too big.

Regards

[high_flyer]

And here is a nice RegEx for email matching:
http://www.regular-expressions.info/email.html

[fengtian.we]

yes , I can ,I can read the file now,

now , this string is a big string, a e-mail address in the string ,

I want get the e-mail address use regular expressions.. How TO

[high_flyer]

READ my last post.

[fengtian.we]

QString str="my name is bob,bobis good boy,i lick bob<";
QRegExp reg("bob");
reg.indexIn(str);
qDebug() << str.count(reg); // output: 3 OK


reg.indexIn(str);
reg.cap(0); // output: "bob" OK
reg.cap(1); // output: "" why
reg.cap(2); // output: "" why

[high_flyer]

Because I think you missunderstood the docs:

Each subsequent element corresponds to the next capturing open left parentheses. Thus cap(1) is the text of the first capturing parentheses, cap(2) is the text of the second, and so on.

So QRegEx::cap(int n) does not retrieve the n'th match, but the match of the n'th parentheses in your expression, and you have only one (n=0) which is why only the first cap() returns a non empty string.

What you are looking for is QRegExp::capturedTexts() I think.

[fengtian.we]

I try it (QRegExp::capturedTexts() ) ,

find one ....

[high_flyer]

what do you mean?
in your last post count() returned 3...
Better if you show your code, and not only explain the end effect.

[fengtian.we]

QString str="my name is bob,bobis good boy,i lick bob<";
QRegExp reg("bob");
reg.indexIn(str);
QStringList list=reg.capturedTexts();
qDebug() << list.count(); // output : 1

[high_flyer]

After a closer reading, it turns out capturedTexts() is not the right method you are looking for:

Some regexps can match an indeterminate number of times. For example if the input string is "Offsets: 12 14 99 231 7" and the regexp, rx, is (\d+)+, we would hope to get a list of all the numbers matched. However, after calling rx.indexIn(str), capturedTexts() will return the list ("12", "12"), i.e. the entire match was "12" and the first subexpression matched was "12". The correct approach is to use cap() in a loop.

[fengtian.we]

I'm read the Qt Assistant yesterday, I thinks should be :

QString str="bob's msn is aa@g.com,and bob's email is qq@aaaa.com.cn :)";
	QRegExp reg("[A-z0-9_\.-]+@[A-z0-9\.]+");
 
	int count=str.count(reg);
	int from=0;
	int in=0;
	QStringList rs;
 
	for(int i=0;i<count;i++)
	{
		in=reg.indexIn(str,from);
		rs.append(reg.cap(0));
		from=in+rs.value(i).size();
	}
 
 
	qDebug() << rs.count();   //output 4(aa@g.com,a@g.com,qq@aaaa.com.cn,q@aaaa.com.cn)
 
	qDebug() << rs.value(0);                        //output "aa@g.com"
	qDebug() << rs.value(1);                       //output "qq@aaaa.com.cn"
	qDebug() << rs.value(2);                        //output ""
	qDebug() << rs.value(3);                        //output ""

QString str="bob's msn is aa@g.com,and bob's email is qq@aaaa.com.cn :)";
	QRegExp reg("[A-z0-9_\.-]+@[A-z0-9\.]+");

	int count=str.count(reg);
	int from=0;
	int in=0;
	QStringList rs;

	for(int i=0;i<count;i++)
	{
		in=reg.indexIn(str,from);
		rs.append(reg.cap(0));
		from=in+rs.value(i).size();
	}


	qDebug() << rs.count();   //output 4(aa@g.com,a@g.com,qq@aaaa.com.cn,q@aaaa.com.cn)

	qDebug() << rs.value(0);                        //output "aa@g.com"
	qDebug() << rs.value(1);                       //output "qq@aaaa.com.cn"
	qDebug() << rs.value(2);                        //output ""
	qDebug() << rs.value(3);                        //output ""

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how about this is that ok?

and please check my regular expressions"[A-z0-9_\.-]+@[A-z0-9\.]+".

[fengtian.we]

OK!!!! Thank you everyone!

this is my way:

QString str="bob's msn is aaa@g.com,and bob's email is qq@aaaa.com.cn :)";
	QRegExp reg("[A-z0-9_\.-]+@[A-z0-9\.]+");
 
	int startPos=0;
	int mailPos=0;
	QStringList rs;
 
	while(true)
	{
		mailPos=reg.indexIn(str,startPos);
		if(mailPos<0)
		{
			break;
		}
		rs.append(reg.cap(0));
		startPos=mailPos+rs.last().size();
	}
 
	qDebug() << rs.count();                     // 2
	qDebug() << rs.value(0);                   // "aaa@g.com"
	qDebug() << rs.value(1);                   // "qq@aaaa.com.cn"

QString str="bob's msn is aaa@g.com,and bob's email is qq@aaaa.com.cn :)";
	QRegExp reg("[A-z0-9_\.-]+@[A-z0-9\.]+");

	int startPos=0;
	int mailPos=0;
	QStringList rs;

	while(true)
	{
		mailPos=reg.indexIn(str,startPos);
		if(mailPos<0)
		{
			break;
		}
		rs.append(reg.cap(0));
		startPos=mailPos+rs.last().size();
	}

	qDebug() << rs.count();                     // 2
	qDebug() << rs.value(0);                   // "aaa@g.com"
	qDebug() << rs.value(1);                   // "qq@aaaa.com.cn"

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haha