How to use QString in Qt

Comments

20 Sep
2009

Article Review by elicec12 (20090920)

This article is very good.

It presents some common methods of QString and systematically mixes an example and a small explanation. The final example might be a bit too complicated for a beginner but the comments describe everything so I think it is ok. I like this final example because one can easily play with it in the simulator.

There is one thing I really miss for a introduction to QString: an explanation of the method QString::arg(). This method is very useful, while QString::append() or QString::prepend() are mostly useless in real applications because of internationalization.

This article is still "Reviewer Approved" for me. It is good even without QString::arg().

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11 Sep
2009

Article Review by fasttrack (20090911)

A string operation is fully described in this article. It’s a good to learn how to perform a particular operation on the string in Qt. at the start the method is described very well.

A small image says everything about the article.

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Article Metadata

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Tested with

Devices(s): Symbian emulator & creator IDE V4.5

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Compatibility

Platform(s): Qt

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Article

Keywords: QString

Created: james1980 (31 Dec 2008)

Last edited: hamishwillee (11 Oct 2012)

This example demonstrates some basic Qt string functions.

Note:Some of images are from qt Creator IDE V4.5 and the code associated with images can also be executed in carbide c++ 2.0

Various Function and Operators

• If you want to append a certain number of identical characters to the string, use operator+=()

QString str = "Hello";
str += QString(10, 'X');

The final content of str is "Hello" followed by ten "X": "HelloXXXXXXXXXX".

• Prepends the string Hello to the beginning of str and returns a reference to this string.

QString str = "world";
str.prepend("Hello ");

The content of str is "Hello world".

• Returns a lowercase copy of the string.

QString str = "HELLO";
QString lowerCase = str.toLower();

The content of lowerCase is "hello". The content of str is still "HELLO", the method QString::toLower() does not modify the string, it returns a lowercase version of the string.

Code snippet using QString

The following example show the use of QString in a graphical application. QLabel is a widget capable of displaying text or images.

#include <QApplication>
#include <QLabel>
#include <QString>
#include <QVBoxLayout>
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
 
    QString str("world");
    QString sizeOfWorld = QString::number(str.size());
 
    // resize the string and removes last two characters
    str.resize(3); // str = "wor"
 
    // Add "Hello " at the beginning
    str.prepend("Hello "); // str = "Hello wor"
 
    // Add "ld" at the end
    str.append("ld"); // str = "Hello world"
 
    // Remove 6 characters at position five, and insert " India" at this position
    str.replace(5, 6, " India");
 
    QLabel *label1 = new QLabel(str);
    QLabel *label2 = new QLabel(sizeOfWorld);
    QVBoxLayout *layout = new QVBoxLayout;
    layout->addWidget(label1);
    layout->addWidget(label2);
 
    QWidget window;
    window.setLayout(layout);
    window.show();
    return app.exec();
}

Here is the result of this code on Microsoft Windows:

Related links:

• Documentation of QString
• How to convert TBuf to QString
• How to convert TBuf to QString