How to use QString in Qt

From Qt Wiki
Jump to navigation Jump to search

Template:ArticleMetaData Template:Abstract

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[edit | edit source]

  • 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[edit | edit source]

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

  1. include <QApplication>
  2. include <QLabel>
  3. include <QString>
  4. 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:

File:String2.JPG

Related links:[edit | edit source]

pt:Archived:Como usar um QString