QString Code examples

http://doc.qt.io/qt-5/qstring.html

int math=100, kor=90, eng=80; 
int res; 
QString strTotal;
 
res = math + kor + eng; 
strTotal = QString::number(res); 
strTotal = QString("strTotal: %1").arg(res);
strTotal.sprintf("strTotal: %d", res); 
strTotal = QString("math: %1, kor: %2, eng: %3, total: %4") .arg(math) .arg(kor) .arg(eng) .arg(res);

qDebug() << "strTotal: " << strTotal; // strTotal: 270

QString str = "Hello";

static const QChar data[4] = { 0x0055, 0x006e, 0x10e3, 0x03a3 };
QString str(data, 4);

QString str;
str.resize(4);

str[0] = QChar('U');
str[1] = QChar('n');
str[2] = QChar(0x10e3);
str[3] = QChar(0x03a3);

QString str;

for (int i = 0; i < str.size(); ++i) {
    if (str.at(i) >= QChar('a') && str.at(i) <= QChar('f'))
        qDebug() << "Found character in range [a-f]";
}

QString str;

if (str == "auto" || str == "extern"
        || str == "static" || str == "register") {
    // ...
}

QString str = "and";
str.prepend("rock ");     // str == "rock and"
str.append(" roll");        // str == "rock and roll"
str.replace(5, 3, "&");   // str == "rock & roll"

QString str = "We must be bold, very bold";
int j = 0;

while ((j = str.indexOf("", j)) != -1) {
    qDebug() << "Found  tag at index position" << j;
    ++j;
}

QString url = QLatin1String("http://www.unicode.org/");

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

    QString foo;
    QString type = "long";

    foo->setText(QLatin1String("vector<") + type + QLatin1String(">::iterator"));

    if (foo.startsWith("(" + type + ") 0x"))
        ...

    #include 

    QString hello("hello");
    QStringRef el(&hello, 2, 3);
    QLatin1String world("world");
    QString message =  hello % el % world % QChar('!');

QString x = "free";
QString y = "dom";

x.append(y);
// x == "freedom"

x.insert(x.size(), y);

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);

QString str;
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"

QString str;
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"

double d = 12.34;
QString str = QString("delta: %1").arg(d, 0, 'E', 3);
// str == "delta: 1.234E+01"

QString str;
str = "%1 %2";

str.arg("%1f", "Hello");        // returns "%1f Hello"
str.arg("%1f").arg("Hello");    // returns "Hellof %2"

QString str;
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"

QString str;
str = "%1%2%3";
str.arg("Hello", QString::number(20), QString::number(50)); // returns "Hello5020"

QString result;
QTextStream(&result) << "pi = " << 3.14;
// result == "pi = 3.14"

QString str("LOGOUT\r\n");
str.chop(2);
// str == "LOGOUT"

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

QString str = "Peter Pan";
str.contains("peter", Qt::CaseInsensitive);    // returns true

QString str = "banana and panama";
str.count(QRegExp("a[nm]a"));    // returns 4

QString str = "banana and panama";
str.count(QRegularExpression("a[nm]a"));    // returns 4

QString str = "Hello world";
QChar *data = str.data();
while (!data->isNull()) {
    qDebug() << data->unicode();
    ++data;
}

QString str = "Bananas";
str.endsWith("anas");         // returns true
str.endsWith("pple");         // returns false

QString str = "Berlin";
str.fill('z');
// str == "zzzzzz"

str.fill('A', 2);
// str == "AA"

QRegExp pattern;
static const QChar unicode[] = {
        0x005A, 0x007F, 0x00A4, 0x0060,
        0x1009, 0x0020, 0x0020};
int size = sizeof(unicode) / sizeof(QChar);

QString str = QString::fromRawData(unicode, size);
if (str.contains(QRegExp(pattern))) {
    // ...
}

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

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

QString str = "the minimum";
str.indexOf(QRegExp("m[aeiou]"), 0);       // returns 4

QString str = "the minimum";
str.indexOf(QRegExp("m[aeiou]"), 0);       // returns 4

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

QString str = "Meal";
str.insert(1, QString("ontr"));
// str == "Montreal"

QString().isEmpty();            // returns true
QString("").isEmpty();          // returns true
QString("x").isEmpty();         // returns false
QString("abc").isEmpty();       // returns false

QString().isNull();             // returns true
QString("").isNull();           // returns false
QString("abc").isNull();        // returns false

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 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(QRegExp("m[aeiou]"));      // returns 8

QString str = "the minimum";
str.lastIndexOf(QRegExp("m[aeiou]"));      // returns 8

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

QString x = "Pineapple";
QString y = x.left(4);      // y == "Pine"

QString s = "apple";
QString t = s.leftJustified(8, '.');    // t == "apple..."

QString str = "Pineapple";
str = str.leftJustified(5, '.', true);    // str == "Pinea"

QString x = "Pineapple";
QStringRef y = x.leftRef(4);        // y == "Pine"

QString x = "Nine pineapples";
QString y = x.mid(5, 4);            // y == "pine"
QString z = x.mid(5);               // z == "pineapples"

QString x = "Nine pineapples";
QStringRef y = x.midRef(5, 4);      // y == "pine"
QStringRef z = x.midRef(5);         // z == "pineapples"

long a = 63;
QString s = QString::number(a, 16);             // s == "3f"
QString t = QString::number(a, 16).toUpper();     // t == "3F"

QString x = "ship";
QString y = "air";
x.prepend(y);
// x == "airship"

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(QRegExp("[aeiou]."));
// r == "The"

QString r = "Telephone";
r.remove(QRegularExpression("[aeiou]."));
// r == "The"

QString str("ab");
str.repeated(4);            // returns "abababab"

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(QRegExp("a[mn]"), "ox");
// s == "Boxoxa"

QString t = "A bon mot.";
t.replace(QRegExp("([^<]*)"), "\\emph{\\1}");
// t == "A \\emph{bon mot}."

QString s = "Banana";
s.replace(QRegularExpression("a[mn]"), "ox");
// s == "Boxoxa"

QString t = "A bon mot.";
t.replace(QRegularExpression("([^<]*)"), "\\emph{\\1}");
// t == "A \\emph{bon mot}."

QString result;
int maxSize;
bool condition;
QChar nextChar;

result.reserve(maxSize);

while (condition)
    result.append(nextChar);

result.squeeze();


QString s = "Hello world";
s.resize(5);
// s == "Hello"

s.resize(8);
// s == "Hello???" (where ? stands for any character)


QString r = "Hello";
r = r.leftJustified(10, ' ');
// r == "Hello     "

QString t = "Hello";
r.resize(t.size() + 10, 'X');
// t == "HelloXXXXXXXXXX"

QString x = "Pineapple";
QString y = x.right(5);      // y == "apple"

QString s = "apple";
QString t = s.rightJustified(8, '.');    // t == "...apple"

QString str = "Pineapple";
str = str.rightJustified(5, '.', true);    // str == "Pinea"

QString x = "Pineapple";
QStringRef y = x.rightRef(5);       // y == "apple"

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 str;
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";
QRegExp sep("\\s+");
str = line.section(sep, 2, 2); // str == "surname"
str = line.section(sep, -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"


QString str;
str.setNum(1234);       // str == "1234"

QString str = "  lots\t of\nwhitespace\r\n ";
str = str.simplified();
// str == "lots of whitespace";

QString str = "World";
int n = str.size();         // n == 5
str.data()[0];              // returns 'W'
str.data()[4];              // returns 'd'
str.data()[5];              // returns '\0'

QString str = "a,,b,c";

QStringList list1 = str.split(',');
// list1: [ "a", "", "b", "c" ]

QStringList list2 = str.split(',', QString::SkipEmptyParts);
// list2: [ "a", "b", "c" ]

QString str;
QStringList list;

str = "Some  text\n\twith  strange whitespace.";
list = str.split(QRegExp("\\s+"));
// list: [ "Some", "text", "with", "strange", "whitespace." ]

str = "This time, a normal English sentence.";
list = str.split(QRegExp("\\W+"), QString::SkipEmptyParts);
// list: [ "This", "time", "a", "normal", "English", "sentence" ]

str = "Now: this sentence fragment.";
list = str.split(QRegExp("\\b"));
// list: [ "", "Now", ": ", "this", " ", "sentence", " ", "fragment", "." ]

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+"), QString::SkipEmptyParts);
// list: [ "This", "time", "a", "normal", "English", "sentence" ]

str = "Now: this sentence fragment.";
list = str.split(QRegularExpression("\\b"));
// list: [ "", "Now", ": ", "this", " ", "sentence", " ", "fragment", "." ]

QString str = "Bananas";
str.startsWith("Ban");     // returns true
str.startsWith("Car");     // returns false

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

bool ok;
double d;

d = QString( "1234.56e-02" ).toDouble(&ok); // ok == true, d == 12.3456

d = QString( "1,234,567.89" ).toDouble(&ok); // ok == false
d = QString( "1234567.89" ).toDouble(&ok); // ok == true

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 plain = "#include "
QString html = plain.toHtmlEscaped();
// html == "#include <QtCore>"

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

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

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


QString str = "The Qt PROJECT";
str = str.toLower();        // str == "the qt project"

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

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

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


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

QString str = "TeXt";
str = str.toUpper();        // str == "TEXT"

QString str = "  lots\t of\nwhitespace\r\n ";
str = str.trimmed();
// str == "lots\t of\nwhitespace"

QString str = "Vladivostok";
str.truncate(4);
// str == "Vlad"

QString x = "free";
QString y = "dom";
x += y;
// x == "freedom"

QString str;

if (str[0] == QChar('?'))
    str[0] = QChar('_');

if (node.hasAttribute("http-contents-length")) //...

if (node.hasAttribute(QStringLiteral("http-contents-length"))) //...

if (attribute.name() == QLatin1String("http-contents-length")) //...

QString s = QStringLiteral("a" "b");

QString a[] = { QStringLiteral("a"), QStringLiteral("b") };