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Qt: преобразование строки в число и числа в строку
20.03.2016
22:41
Текстовые метки: qt, преобразование типов, текст, строка, число, SQtring, int
Раздел: Компьютер - Программирование - Язык C++ - Библиотека Qt - Принципы написания кода

Преобразование числа в строку

QString & QString::setNum(int n, int base = 10)

Sets the string to the printed value of n in the specified base, and returns a reference to the string.

The base is 10 by default and must be between 2 and 36. For bases other than 10, n is treated as an unsigned integer.


QString str;

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


The formatting always uses QLocale::C, i.e., English/UnitedStates. To get a localized string representation of a number, use QLocale::toString() with the appropriate locale.


Преобразование строки в целое число

int QString::toInt(bool * ok = 0, int base = 10) const

Returns the string converted to an int using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.

If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.

If base is 0, the C language convention is used: If the string begins with "0x", base 16 is used; if the string begins with "0", base 8 is used; otherwise, base 10 is used.

The string conversion will always happen in the 'C' locale. For locale dependent conversion use QLocale::toInt()

Example:

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


Преобразование строки в вещественное число

float QString::toFloat(bool * ok = 0) const

Returns the string converted to a float value.

If a conversion error occurs, *ok is set to false; otherwise *ok is set to true. Returns 0.0 if the conversion fails.

The string conversion will always happen in the 'C' locale. For locale dependent conversion use QLocale::toFloat()

Example:

QString str1 = "1234.56";

str1.toFloat(); // returns 1234.56


bool ok;

QString str2 = "R2D2";

str2.toFloat(&ok); // returns 0.0, sets ok to false


Преобразование строки в вещественное число двойной точности

double QString::toDouble(bool * ok = 0) const

Returns the string converted to a double value. Returns 0.0 if the conversion fails.

If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.

QString str = "1234.56";

double val = str.toDouble(); // val == 1234.56

Various string formats for floating point numbers can be converted to double values:

bool ok;

double d;

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

The string conversion will always happen in the 'C' locale. For locale dependent conversion use QLocale::toDouble()

d = QString( "1234,56" ).toDouble(&ok); // ok == false

d = QString( "1234.56" ).toDouble(&ok); // ok == true, d == 1234.56

For historic reasons, this function does not handle thousands group separators. If you need to convert such numbers, use QLocale::toDouble().

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

d = QString( "1234567.89" ).toDouble(&ok); // ok == true


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