Using variables ending with numbers

phil63

Hi,

I deal with a bunch of variables named:
nom1, nom2, nom3, nom4,.....
I would like to call the variable (nomX).
I tried :
@
("nom%1).arg(X)="Sam";
(QString("nom%1).arg(X))="Sam";
@
but with no success.

Could you tell me how to do it.
Thank you

koahnig

According to the docs of Qt5 it would more like:
@
QString str;
str = "nom%1";

str.arg("", "X");
@

[edit, running into an issue with the editor here.
the first argument of str.arg shall be "% 1 f" without spaces. ]

However, I am not sure it looks stupid and might be wrong in the docs. I do not use QString very often, more the std::string variant.

But this should work:
@
QString str;
str = "nom";
QString str2 = str + QString ("X");
@
or
@
QString str;
str = "nom";
QString str2 = str + "X";
@

phil63

Hi,
Thank you for your reply.
My request was not clear. Let me put it that way:

@
in header
QString nom1;
QString nom2;
@
@
in .cpp
nom1="Sam"
nom2"Pierre";

QString st="nom";
QString st2=st+"1";
st2="Paul";
// nom1 should now be : Paul - but it isn't , only st2="Paul"
@

DerManu

@QStringList nom;
nom.append("Sam");
nom.append("Pierre");

QString someOtherString = nom.at(0); // will be "Sam"@

This isn't a scripting language, so building variable identifiers from strings is rightly discouraged, for performance, security and anti-spaghetti-code reasons. Through hackery (a.k.a. meta object system), it is possible though. But don't do it. Leads to bad programs, and we've got plenty of those.

koahnig

As already explained by DerManu.

Or you may use "QMap":http://qt-project.org/doc/qt-5.0/qtcore/qmap.html .
@
QMap<QString, QString> myMap;
myMap["nom1"]="Sam";
myMap["nom2"]="Pierre";
myMap["nom3"]="Paul";

QString st = "nom";
QString st2 = st + "1";

qDebug() << myMap[st2];
@
should work.

DerManu

@koahnig, I slightly disagree with the QMap usage here. Because that number in the end of "nom" just screams for an integer index based container like QVector or QList (@phil: QStringList is just QList<QString>), and so one should use them, and not the more key-generic QMap<QString, QString>. If non-continuous index ranges are needed, QMap<int, QString> would be okay.

koahnig

[quote author="DerManu" date="1371374572"]@koahnig, I slightly disagree with the QMap usage here. Because that number in the end of "nom" just screams for an integer index based container like QVector or QList (@phil: QStringList is just QList<QString>), and so one should use them, and not the more key-generic QMap<QString, QString>. If non-continuous index ranges are needed, QMap<int, QString> would be okay.[/quote]
Yes, you are right, but the question is what is the real case at the end. If it is a simplified example and the names will be a bit more complex and not just a number appended, it might make sense.

phil63

Thank you to both of you

AdamHynes

This post is deleted!

JonB

@AdamHynes ...Might interfere with people's ability to write good Qt code... ;-)

Christian Ehrlicher

This post is deleted!