How do I populate values of a static QMap in C++ Qt?

Question

I have this in my C++ header file:

#include <QMap>
#include <QString>

class LogEvent {

public:
    LogEvent();

    enum column_t {TIMESTAMP_COLUMN = 0, TYPE_COLUMN = 1, EVENT_COLUMN = 2,
        FILE_COLUMN = 3};
    static QMap<column_t, QString> COLUMN_NAMES;

    static QMap<column_t, QString> getColumnNames() {
        return LogEvent::COLUMN_NAMES;
    }

    //blah blah blah other functions
};

This is my C++ source file:

#include "LogEvent.h"

LogEvent::LogEvent()
{
    //constructor code
}

//blah blah blah other functions

I want to add values to my static QMap COLUMN_NAMES. Where and how would I do this?

Answer 1

You can use static function that returns initialized map:

// source file:
QMap<column_t, QString> LogEvent::initColumnNames() {
    QMap<column_t, QString> map;
    map.insert(LogEvent::TIMESTAMP_COLUMN,"Timestamp");
    // and so on
    return map;
}

QMap<column_t, QString> LogEvent::COLUMN_NAMES = initColumnNames();

Also, in case you want to use strings internationalization in static variables and need to call QTextCodec::setCodecForTr first, it is a good idea to move static variable into its getter function:

class LogEvent {

public:
// ...
    static QMap<column_t, QString> initColumnNames();

    static QMap<column_t, QString> getColumnNames() {
        static QMap<column_t, QString> COLUMN_NAMES = initColumnNames();
        return COLUMN_NAMES;
    }
}

This way COLUMN_NAMES will be initialized with the first call of getColumnNames() and you can set the text codec beforehand. But this is not thread-safe.