main.cpp

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** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the documentation of the Qt Toolkit.
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#include <QtGui>
#include <QApplication>
#include <stdio.h>
 
class Widget : public QWidget
{
public:
    Widget(QWidget *parent = nullptr);
 
    void constCharPointer();
    void constCharArray();
    void characterReference();
    void atFunction();
    void stringLiteral();
    void modify();
    void index();
    QString boolToString(bool b);
    void nullVsEmpty();
 
    void appendFunction();
    void argFunction();
    void chopFunction();
    void compareFunction();
    void compareSensitiveFunction();
    void containsFunction();
    void countFunction();
    void dataFunction();
    void endsWithFunction();
    void fillFunction();
    void fromRawDataFunction();
 
    void indexOfFunction();
    void firstIndexOfFunction();
    void insertFunction();
    void isNullFunction();
    void isEmptyFunction();
    void lastIndexOfFunction();
    void firstFunction();
    void leftJustifiedFunction();
    void slicedFunction();
    void numberFunction();
 
    void prependFunction();
    void removeFunction();
    void replaceFunction();
    void reserveFunction();
    void resizeFunction();
    void lastFunction();
    void rightJustifiedFunction();
    void sectionFunction();
    void setNumFunction();
    void simplifiedFunction();
 
    void sizeFunction();
    void splitFunction();
    void splitCaseSensitiveFunction();
    void sprintfFunction();
    void startsWithFunction();
    void toDoubleFunction();
    void toFloatFunction();
    void toIntFunction();
    void toLongFunction();
    void toLongLongFunction();
 
    void toLowerFunction();
    void toShortFunction();
    void toUIntFunction();
    void toULongFunction();
    void toULongLongFunction();
    void toUShortFunction();
    void toUpperFunction();
    void trimmedFunction();
    void truncateFunction();
 
    void plusEqualOperator();
    void arrayOperator();
};
 
Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
}
 
void Widget::constCharPointer()
{
    QString str = "Hello";
}
 
void Widget::constCharArray()
{
    static const QChar data[4] = { 0x0055, 0x006e, 0x10e3, 0x03a3 };
    QString str(data, 4);
}
 
void Widget::characterReference()
{
    QString str;
    str.resize(4);
 
    str[0] = QChar('U');
    str[1] = QChar('n');
    str[2] = QChar(0x10e3);
    str[3] = QChar(0x03a3);
}
 
void Widget::atFunction()
{
    QString str;
 
    for (qsizetype i = 0; i < str.size(); ++i) {
        if (str.at(i) >= QChar('a') && str.at(i) <= QChar('f'))
            qDebug() << "Found character in range [a-f]";
    }
}
 
void Widget::stringLiteral()
{
    QString str;
 
    if (str == "auto" || str == "extern"
            || str == "static" || str == "register") {
        // ...
    }
}
 
void Widget::modify()
{
    QString str = "and";
    str.prepend("rock ");     // str == "rock and"
    str.append(" roll");        // str == "rock and roll"
    str.replace(5, 3, "&");   // str == "rock & roll"
}
 
void Widget::index()
{
    QString str = "We must be <b>bold</b>, very <b>bold</b>";
    qsizetype j = 0;
 
    while ((j = str.indexOf("<b>", j)) != -1) {
        qDebug() << "Found <b> tag at index position" << j;
        ++j;
    }
}
 
QString Widget::boolToString(bool b)
{
    QString result;
    if (b)
        result = "True";
    else
        result = "False";
    return result;
}
 
 
void Widget::nullVsEmpty()
{
    QString().isNull();               // returns true
    QString().isEmpty();              // returns true
 
    QString("").isNull();             // returns false
    QString("").isEmpty();            // returns true
 
    QString("abc").isNull();          // returns false
    QString("abc").isEmpty();         // returns false
}
 
void Widget::appendFunction()
{
    QString x = "free";
    QString y = "dom";
 
    x.append(y);
    // x == "freedom"
 
    x.insert(x.size(), y);
}
 
void Widget::argFunction()
{
    QString i;           // current file's number
    QString total;       // number of files to process
    QString fileName;    // current file's name
 
    QString status = QString("Processing file %1 of %2: %3")
                    .arg(i).arg(total).arg(fileName);
 
    {
    int i;                // current file's number
    int total;            // number of files to process
    QStringView fileName; // current file's name
 
    QString status = QString("Processing file %1 of %2: %3")
                    .arg(i).arg(total).arg(fileName);
    }
 
    QString str;
    str = "%1 %2";
 
    str.arg("%1f", "Hello");        // returns "%1f Hello"
    str.arg("%1f").arg("Hello");    // returns "Hellof %2"
 
    str = "%1%3%2";
    str.arg("Hello").arg(20).arg(50); // returns "Hello500"
 
    str = "%1%2%3";
    str.arg("Hello").arg(50).arg(20); // returns "Hello5020"
 
    str = "%1%3%2";
    str.arg("Hello", QString::number(20), QString::number(50)); // returns "Hello5020"
 
    str = QString("Decimal 63 is %1 in hexadecimal")
            .arg(63, 0, 16);
    // str == "Decimal 63 is 3f in hexadecimal"
 
    QLocale::setDefault(QLocale(QLocale::English, QLocale::UnitedStates));
    str = QString("%1 %L2 %L3")
            .arg(12345)
            .arg(12345)
            .arg(12345, 0, 16);
    // str == "12345 12,345 3039"
}
 
void Widget::chopFunction()
{
    QString str("LOGOUT\r\n");
    str.chop(2);
    // str == "LOGOUT"
}
 
void Widget::compareFunction()
{
    int x = QString::compare("auto", "auto");   // x == 0
    int y = QString::compare("auto", "car");    // y < 0
    int z = QString::compare("car", "auto");    // z > 0
}
 
void Widget::compareSensitiveFunction()
{
    int x = QString::compare("aUtO", "AuTo", Qt::CaseInsensitive);  // x == 0
    int y = QString::compare("auto", "Car", Qt::CaseSensitive);     // y > 0
    int z = QString::compare("auto", "Car", Qt::CaseInsensitive);   // z < 0
 
    int x = QtPrivate::compareStrings(u"aUtO", u"AuTo", Qt::CaseInsensitive);  // x == 0
    int y = QtPrivate::compareStrings(u"auto", u"Car", Qt::CaseSensitive);     // y > 0
    int z = QtPrivate::compareStrings(u"auto", u"Car", Qt::CaseInsensitive);   // z < 0
}
 
void Widget::containsFunction()
{
    QString str = "Peter Pan";
    str.contains("peter", Qt::CaseInsensitive);    // returns true
}
 
void Widget::countFunction()
{
    QString str = "banana and panama";
    str.count(QRegularExpression("a[nm]a"));    // returns 4
}
 
void Widget::dataFunction()
{
    QString str = "Hello world";
    QChar *data = str.data();
    while (!data->isNull()) {
        qDebug() << data->unicode();
        ++data;
    }
}
 
void Widget::endsWithFunction()
{
    QString str = "Bananas";
    str.endsWith("anas");         // returns true
    str.endsWith("pple");         // returns false
}
 
void Widget::fillFunction()
{
    QString str = "Berlin";
    str.fill('z');
    // str == "zzzzzz"
 
    str.fill('A', 2);
    // str == "AA"
}
 
void Widget::fromRawDataFunction()
{
    QRegularExpression pattern("\u00A4");
    static const QChar unicode[] = {
            0x005A, 0x007F, 0x00A4, 0x0060,
            0x1009, 0x0020, 0x0020};
    qsizetype size = sizeof(unicode) / sizeof(QChar);
 
    QString str = QString::fromRawData(unicode, size);
    if (str.contains(pattern) {
        // ...
    }
}
 
void Widget::indexOfFunction()
{
    QString x = "sticky question";
    QString y = "sti";
    x.indexOf(y);               // returns 0
    x.indexOf(y, 1);            // returns 10
    x.indexOf(y, 10);           // returns 10
    x.indexOf(y, 11);           // returns -1
}
 
void Widget::firstIndexOfFunction()
{
    QString str = "the minimum";
    str.indexOf(QRegularExpression("m[aeiou]"), 0);       // returns 4
 
    QString str = "the minimum";
    QRegularExpressionMatch match;
    str.indexOf(QRegularExpression("m[aeiou]"), 0, &match);       // returns 4
    // match.captured() == mi
}
 
void Widget::insertFunction()
{
    QString str = "Meal";
    str.insert(1, QString("ontr"));
    // str == "Montreal"
}
 
void Widget::isEmptyFunction()
{
    QString().isEmpty();            // returns true
    QString("").isEmpty();          // returns true
    QString("x").isEmpty();         // returns false
    QString("abc").isEmpty();       // returns false
}
 
void Widget::isNullFunction()
{
    QString().isNull();             // returns true
    QString("").isNull();           // returns false
    QString("abc").isNull();        // returns false
}
 
void Widget::lastIndexOfFunction()
{
    QString x = "crazy azimuths";
    QString y = "az";
    x.lastIndexOf(y);           // returns 6
    x.lastIndexOf(y, 6);        // returns 6
    x.lastIndexOf(y, 5);        // returns 2
    x.lastIndexOf(y, 1);        // returns -1
 
    QString str = "the minimum";
    str.lastIndexOf(QRegularExpression("m[aeiou]"));      // returns 8
 
    QString str = "the minimum";
    QRegularExpressionMatch match;
    str.lastIndexOf(QRegularExpression("m[aeiou]"), -1, &match);      // returns 8
    // match.captured() == mu
}
 
void Widget::firstFunction()
{
    QString x = "Pineapple";
    QString y = x.first(4);      // y == "Pine"
}
 
void Widget::leftJustifiedFunction()
{
    QString s = "apple";
    QString t = s.leftJustified(8, '.');    // t == "apple..."
 
    QString str = "Pineapple";
    str = str.leftJustified(5, '.', true);    // str == "Pinea"
}
 
void Widget::slicedFunction()
{
    QString x = "Nine pineapples";
    QString y = x.sliced(5, 4);            // y == "pine"
    QString z = x.sliced(5);               // z == "pineapples"
}
 
void Widget::numberFunction()
{
    long a = 63;
    QString s = QString::number(a, 16);             // s == "3f"
    QString t = QString::number(a, 16).toUpper();     // t == "3F"
}
 
void Widget::prependFunction()
{
    QString x = "ship";
    QString y = "air";
    x.prepend(y);
    // x == "airship"
}
 
void Widget::removeFunction()
{
    QString s = "Montreal";
    s.remove(1, 4);
    // s == "Meal"
 
    QString t = "Ali Baba";
    t.remove(QChar('a'), Qt::CaseInsensitive);
    // t == "li Bb"
 
    QString r = "Telephone";
    r.remove(QRegularExpression("[aeiou]."));
    // r == "The"
}
 
void Widget::replaceFunction()
{
    QString x = "Say yes!";
    QString y = "no";
    x.replace(4, 3, y);
    // x == "Say no!"
 
    QString str = "colour behaviour flavour neighbour";
    str.replace(QString("ou"), QString("o"));
    // str == "color behavior flavor neighbor"
 
    QString equis = "xxxxxx";
    equis.replace("xx", "x");
    // equis == "xxx"
 
    QString s = "Banana";
    s.replace(QRegularExpression("a[mn]"), "ox");
    // s == "Boxoxa"
 
    QString t = "A <i>bon mot</i>.";
    t.replace(QRegularExpression("<i>([^<]*)</i>"), "\\emph{\\1}");
    // t == "A \\emph{bon mot}."
}
 
void Widget::reserveFunction()
{
    QString result;
    qsizetype maxSize;
    bool condition;
    QChar nextChar;
 
    result.reserve(maxSize);
 
    while (condition)
        result.append(nextChar);
 
    result.squeeze();
}
 
void Widget::resizeFunction()
{
    QString s = "Hello world";
    s.resize(5);
    // s == "Hello"
 
    s.resize(8);
    // s == "Hello???" (where ? stands for any character)
 
    QString t = "Hello";
    r.resize(t.size() + 10, 'X');
    // t == "HelloXXXXXXXXXX"
 
    QString r = "Hello";
    r = r.leftJustified(10, ' ');
    // r == "Hello     "
}
 
void Widget::lastFunction()
{
    QString x = "Pineapple";
    QString y = x.last(5);      // y == "apple"
}
 
void Widget::rightJustifiedFunction()
{
    QString s = "apple";
    QString t = s.rightJustified(8, '.');    // t == "...apple"
 
    QString str = "Pineapple";
    str = str.rightJustified(5, '.', true);    // str == "Pinea"
}
 
void Widget::sectionFunction()
{
    QString str;
    QString csv = "forename,middlename,surname,phone";
    QString path = "/usr/local/bin/myapp"; // First field is empty
    QString::SectionFlag flag = QString::SectionSkipEmpty;
 
 
    str = csv.section(',', 2, 2);   // str == "surname"
    str = path.section('/', 3, 4);  // str == "bin/myapp"
    str = path.section('/', 3, 3, flag); // str == "myapp"
 
    str = csv.section(',', -3, -2);  // str == "middlename,surname"
    str = path.section('/', -1); // str == "myapp"
 
    QString data = "forename**middlename**surname**phone";
 
    str = data.section("**", 2, 2); // str == "surname"
    str = data.section("**", -3, -2); // str == "middlename**surname"
 
    QString line = "forename\tmiddlename  surname \t \t phone";
    QRegularExpression sep("\\s+");
    str = line.section(sep, 2, 2); // str == "surname"
    str = line.section(sep, -3, -2); // str == "middlename  surname"
}
 
void Widget::setNumFunction()
{
    QString str;
    str.setNum(1234);       // str == "1234"
}
 
void Widget::simplifiedFunction()
{
    QString str = "  lots\t of\nwhitespace\r\n ";
    str = str.simplified();
    // str == "lots of whitespace";
}
 
void Widget::sizeFunction()
{
    QString str = "World";
    qsizetype n = str.size();   // n == 5
    str.data()[0];              // returns 'W'
    str.data()[4];              // returns 'd'
}
 
void Widget::splitFunction()
{
    QString str;
    QStringList list;
 
    str = "Some  text\n\twith  strange whitespace.";
    list = str.split(QRegularExpression("\\s+"));
    // list: [ "Some", "text", "with", "strange", "whitespace." ]
 
    str = "This time, a normal English sentence.";
    list = str.split(QRegularExpression("\\W+"), Qt::SkipEmptyParts);
    // list: [ "This", "time", "a", "normal", "English", "sentence" ]
 
    str = "Now: this sentence fragment.";
    list = str.split(QRegularExpression("\\b"));
    // list: [ "", "Now", ": ", "this", " ", "sentence", " ", "fragment", "." ]
}
 
void Widget::splitCaseSensitiveFunction()
{
    QString str = QStringLiteral("a,,b,c");
 
    QStringList list1 = str.split(QLatin1Char(','));
    // list1: [ "a", "", "b", "c" ]
 
    QStringList list2 = str.split(QLatin1Char(','), Qt::SkipEmptyParts);
    // list2: [ "a", "b", "c" ]
 
    QString str = "abc";
    auto parts = str.split(QString());
    // parts: {"", "a", "b", "c", ""}
 
    QString str = "/a/b/c/";
    auto parts = str.split(QLatin1Char('/'));
    // parts: {"", "a", "b", "c", ""}
}
 
void Widget::sprintfFunction()
{
    QString result;
    QTextStream(&result) << "pi = " << 3.14;
    // result == "pi = 3.14"
}
 
void Widget::startsWithFunction()
{
    QString str = "Bananas";
    str.startsWith("Ban");     // returns true
    str.startsWith("Car");     // returns false
}
 
void Widget::toDoubleFunction()
{
    QString str = "1234.56";
    double val = str.toDouble();   // val == 1234.56
 
    bool ok;
    double d;
 
    d = QString( "1234.56e-02" ).toDouble(&ok); // ok == true, d == 12.3456
 
    d = QString( "1234.56e-02 Volt" ).toDouble(&ok); // ok == false, d == 0
 
    d = QString( "1234,56" ).toDouble(&ok); // ok == false
    d = QString( "1234.56" ).toDouble(&ok); // ok == true, d == 1234.56
 
    d = QString( "1,234,567.89" ).toDouble(&ok); // ok == false
    d = QString( "1234567.89" ).toDouble(&ok); // ok == true
}
 
void Widget::toFloatFunction()
{
    QString str1 = "1234.56";
    str1.toFloat();             // returns 1234.56
 
    bool ok;
    QString str2 = "R2D2";
    str2.toFloat(&ok);          // returns 0.0, sets ok to false
 
    QString str3 = "1234.56 Volt";
    str3.toFloat(&ok);          // returns 0.0, sets ok to false
}
 
void Widget::toIntFunction()
{
    QString str = "FF";
    bool ok;
    int hex = str.toInt(&ok, 16);       // hex == 255, ok == true
    int dec = str.toInt(&ok, 10);       // dec == 0, ok == false
}
 
void Widget::toLongFunction()
{
    QString str = "FF";
    bool ok;
 
    long hex = str.toLong(&ok, 16);     // hex == 255, ok == true
    long dec = str.toLong(&ok, 10);     // dec == 0, ok == false
}
 
void Widget::toLongLongFunction()
{
    QString str = "FF";
    bool ok;
 
    qint64 hex = str.toLongLong(&ok, 16);      // hex == 255, ok == true
    qint64 dec = str.toLongLong(&ok, 10);      // dec == 0, ok == false
}
 
void Widget::toLowerFunction()
{
    QString str = "The Qt PROJECT";
    str = str.toLower();        // str == "the qt project"
}
 
void Widget::toShortFunction()
{
    QString str = "FF";
    bool ok;
 
    short hex = str.toShort(&ok, 16);   // hex == 255, ok == true
    short dec = str.toShort(&ok, 10);   // dec == 0, ok == false
}
 
void Widget::toUIntFunction()
{
    QString str = "FF";
    bool ok;
 
    uint hex = str.toUInt(&ok, 16);     // hex == 255, ok == true
    uint dec = str.toUInt(&ok, 10);     // dec == 0, ok == false
}
 
void Widget::toULongFunction()
{
    QString str = "FF";
    bool ok;
 
    ulong hex = str.toULong(&ok, 16);   // hex == 255, ok == true
    ulong dec = str.toULong(&ok, 10);   // dec == 0, ok == false
}
 
void Widget::toULongLongFunction()
{
    QString str = "FF";
    bool ok;
 
    quint64 hex = str.toULongLong(&ok, 16);    // hex == 255, ok == true
    quint64 dec = str.toULongLong(&ok, 10);    // dec == 0, ok == false
}
 
void Widget::toUShortFunction()
{
    QString str = "FF";
    bool ok;
 
    ushort hex = str.toUShort(&ok, 16);     // hex == 255, ok == true
    ushort dec = str.toUShort(&ok, 10);     // dec == 0, ok == false
}
 
void Widget::toUpperFunction()
{
    QString str = "TeXt";
    str = str.toUpper();        // str == "TEXT"
}
 
void Widget::trimmedFunction()
{
    QString str = "  lots\t of\nwhitespace\r\n ";
    str = str.trimmed();
    // str == "lots\t of\nwhitespace"
}
 
void Widget::truncateFunction()
{
    QString str = "Vladivostok";
    str.truncate(4);
    // str == "Vlad"
}
 
void Widget::plusEqualOperator()
{
    QString x = "free";
    QString y = "dom";
    x += y;
    // x == "freedom"
}
 
void Widget::arrayOperator()
{
    QString str;
 
    if (str[0] == QChar('?'))
        str[0] = QChar('_');
}
 
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    Widget widget;
    widget.show();
    return app.exec();
}