Home » C++ » Convert an int to a QString with zero padding (leading zeroes)

Convert an int to a QString with zero padding (leading zeroes)

Posted by: admin November 29, 2017 Leave a comment

Questions:

I want to “stringify” a number and add zero-padding, like how printf("%05d") would add leading zeros if the number is less than 5 digits.

Answers:

Use this:

QString number = QString("%1").arg(yourNumber, 5, 10, QChar('0'));

5 here corresponds to 5 in printf("%05d"). 10 is the radix, you can put 16 to print the number in hex.

Questions:
Answers:

QString QString::rightJustified ( int width, QChar fill = QLatin1Char( ‘ ‘ ), bool truncate = false ) const

int myNumber = 99;
QString result;
result = QString::number(myNumber).rightJustified(5, '0');

result is now 00099

Questions:
Answers:

The Short Example:

int myNumber = 9;

//Arg1: the number
//Arg2: how many 0 you want?
//Arg3: The base (10 - decimal, 16 hexadecimal - if you don't understand, choose 10)
//      It seems like only decimal can support negative numbers.
QString number = QString("%1").arg(myNumber, 2, 10, QChar('0')); 

Output will be: 09

Questions:
Answers:

Try:

QString s = s.sprintf("%08X",yournumber);

EDIT:
According to the docs at http://qt-project.org/doc/qt-4.8/qstring.html#sprintf:

Warning: We do not recommend using QString::sprintf() in new Qt code. Instead, consider using QTextStream or arg(), both of which support Unicode strings seamlessly and are type-safe. Here’s an example that uses QTextStream:

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

Read the other docs for features missing from this method.

Questions:
Answers:

I was trying this (which does work, but cumbersome).

QString s;
s.setNum(n,base);
s = s.toUpper();
presision -= s.length();
while(presision>0){
    s.prepend('0');
    presision--;
}

Questions:
Answers:

I use a technique since VB 5

QString theStr=QString("0000%1").arg(theNumber).right(4);