Insertion double quote into string/qstring

Hello, I have this code:

Code:

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// query string;
    QString queryString("SELECT * FROM merchandize WHERE PicPath="%1";");
    queryString.arg(strPicPath);

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Once I try to compile it, I get following error:

Code:

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CMerchandizeBrowser.cpp: In member function `QString CMerchandizeBrowser::getMerchandizeName(QString)':
CMerchandizeBrowser.cpp:330: error: invalid operands of types `const char[41]' and `int' to binary `operator%'

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I need those quotes because SQL syntax. Please help!

See Escape character

Ok, but code:

Code:

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Q_ASSERT(strPicPath.size()>0);    // assertion test //
query string;
QString queryString("SELECT * FROM merchandize WHERE PicPath=\"%1\";");
QueryString.arg(strPicPath);
qDebug() << "queryString: " << queryString;    // debug

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in the last line (qDebug) reports:

Code:

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queryString:  "SELECT * FROM merchandize WHERE PicPath="%1";"

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which is not ok, instead of '%1' there should be the contens of paramaterer strPicPath. I do not get it.

QString::arg() returns a copy of the string where the replacements have been done.

So, it is ok then?

Are you using the return value of QString::arg()? It's an ordinary function which returns a value.

Yep, I do. Let me give you complete code:

Code:

---

QString CMerchandizeBrowser::getMerchandizeName(QString strPicPath)
{
    Q_ASSERT(strPicPath.size()>0);    // assertion test
    // query string;
    QString queryString("SELECT * FROM merchandize WHERE PicPath=\"%1\";");
    queryString.arg(strPicPath);
    qDebug() << "queryString: " << queryString;    // debug
 
    QSqlQuery query;    // sql query 
    query.exec(queryString);    // executes query
    Q_ASSERT(query.value(iMerchandizeFieldNAME).toString().size()>0);    // assertion test
    qDebug() << query.value(iMerchandizeFieldNAME).toString();    // debug
    return(query.value(iMerchandizeFieldNAME).toString());    // returns merchandize name
}

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Quote:

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Originally Posted by MarkoSan

Yep, I do. Let me give you complete code:

Code:

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[...]
queryString.arg(strPicPath);
[...]

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To me it looks you don't. Notice that QString::arg() is a const method. Again, it does not modify the original value but returns a modified value.

I have this system everywhere in project and it works fine, just here it does not work. So, how should I rewrite the code, have you any clues?

Quote:

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Originally Posted by MarkoSan

I have this system everywhere in project and it works fine, just here it does not work. So, how should I rewrite the code, have you any clues?

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Give yourself a moment to think it. Consider the following piece of pseudo code:

Code:

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QString QString::arg(value) const
{
    // does not modify _this_ but returns a copy
    QString copy(*this);
    copy.replacePlaceHolderWithValue(value);
    return copy;
}

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What's the content of foo?

Code:

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QString foo("%1");
foo.arg(1234);

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What's the content of bar?

Code:

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QString bar("%1");
bar = bar.arg(5678);

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foo has 1234

and bar has 5678

Am I right?

Quote:

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Originally Posted by MarkoSan

foo has 1234

and bar has 5678

Am I right?

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Unfortunately not (foo has "%1" and bar has "5678"). However, did you notice the difference? Looks subtle, but is in fact significant.

Aha, I must use = operator to set right value. God damn, thanks. :confused: