How do I append characters of a QString to another QString in a neat way?

legitnameyo

I've got the following code and it doesn't really look all that pretty to me

QString current_t = QDateTime::currentDateTime().toString("yyyyMMddhmmss"); // the current time and date

QString  yyyy, MM, dd, h, min, sec = ""; // years, month, day, hour, minutes, seconds

        if(current_t.length() == 13) { // used to make the time for the hour to e.g. 05 instead of just 5
            current_t.insert(8, "0");
        }
        // year
        yyyy += current_t[0];
        yyyy += current_t[1];
        yyyy += current_t[2];
        yyyy += current_t[3];
        // month        
        MM += current_t[4];
        MM += current_t[5];
        // day
        dd += current_t[6];
        dd += current_t[7];
        // hour
        h += current_t[8];
        h += current_t[9];
        // minute
        min += current_t[10];
        min += current_t[11];
        // second
        sec += current_t[12];
        sec += current_t[13];

is there any more efficient way of doing this?

JKSH

@legitnameyo said in How do I append characters of a QString to another QString in a neat way?:

    if(current_t.length() == 13) { // used to make the time for the hour to e.g. 05 instead of just 5
        current_t.insert(8, "0");
    }

If you want 05 instead of 5, then use hh or HH. Don't use h.

QDateTime::currentDateTime().toString("yyyyMMddHHmmss")

   // year
   yyyy += current_t[0];
   yyyy += current_t[1];
   yyyy += current_t[2];
   yyyy += current_t[3];

See https://doc.qt.io/qt-5/qstring.html#mid : yyyy = current_t.mid(0, 4);

QString  yyyy, MM, dd, h, min, sec = "";

Don't initialize a QString with = "".

QString yyyy1 = ""; // Bad. Wastes CPU cycles.

QString yyyy2;      // Good. It is automatically initialized to a null string

Anyway, you could simplify the whole thing:

QDateTime now = QDateTime::currentDateTime();

QString yyyy = now.toString("yyyy");
QString MM = now.toString("MM");
QString dd = now.toString("dd");
QString HH = now.toString("HH");
QString mm = now.toString("mm");
QString ss = now.toString("ss");

Kent-Dorfman

there are many better ways to do this:

use regular expressions to parse the date/time string
QString::mid() method
.
.
.

jsulm

@legitnameyo said in How do I append characters of a QString to another QString in a neat way?:

is there any more efficient way of doing this?

Yes, use QString::mid, https://doc.qt.io/qt-5/qstring.html#mid

QString  yyyy = current_t.mid(0, 4);
QString MM = current_t.mid(3, 2);
...

Kent-Dorfman

@JKSH said in How do I append characters of a QString to another QString in a neat way?:

Anyway, you could simplify the whole thing:
QDateTime now = QDateTime::currentDateTime();

QString yyyy = now.toString("yyyy");
QString MM = now.toString("MM");
QString dd = now.toString("dd");
QString HH = now.toString("HH");
QString mm = now.toString("mm");
QString ss = now.toString("ss");

This is ideally the best general solution, IMHO