Appending number to QString with arg() , is there better ways?

Question

I've been using QString::number () to convert numbers to string for long time , now i'm wondering if there's something better than following:

  int i = 0;
  QString msg = QString ("Loading %1").arg (QString::number (i));

How can i spare QString::number () ? i checked document , seems only "%1" is applicable , no other stuff like "%d" could work

Answer 1

You can directly use arg() like this

int i = 0;
QString msg = QString ("Loading %1").arg(i);

Qt will automatically convert it for you

Answer 2

QString's arg() function does indeed implement many different types and automatically detect what you provide it. Providing multiple parameters to a single arg() call like so

// Outputs "one two three"
QString s = QString("%1 %2 %3").arg("one", "two", "three")

is only implemented for QString (and hence const char*) parameters.

However, you can chain arg calls together and still use the numbering system:

int i = 5;
size_t ui = 6;
int j = 12;
// Outputs "int 5 size_t 6 int 12"
qDebug() << QString("int %1 size_t  %2 int%3").arg(i).arg(ui).arg(j);
// Also outputs "int 5 size_t 6 int 12"
qDebug() << QString("int %1 int %3 size_t %2").arg(i).arg(j).arg(ui);

Answer 3

Take a look at QString documentation. You have plenty of ::arg method overloads, that take different types. QString doesn't need to know what type will be under %n, method replacing that %n will know it and put proper value.