C ++是否可以延迟恒定静态成员的初始化? [英] C++ is it possible to delay initialization of constant static member?

问题描述

我正在使用Qt，但这是一个通用的C ++问题.我的情况很简单，我有一个Constants类，它具有一个恒定的静态成员，我希望在进行某些函数调用后对其进行初始化.

I am using Qt but this is a generic C++ question. My case is simple, I have a class Constants which has a constant static member which I want it to be initialized after certain function calls are made.

Constants.h

Constants.h

#ifndef CONSTANTS_H
#define CONSTANTS_H

class Constants
{
public:

    static const char* const FILE_NAME;
};

#endif // CONSTANTS_H

Constants.cpp

Constants.cpp

#include "constants.h"
#include <QApplication>

const char* const Constants::FILE_NAME = QApplication::applicationFilePath().toStdString().c_str();

main.cpp

#include <QtGui/QApplication>
#include "mainwindow.h"
#include "constants.h"
#include <QDebug>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    qDebug()<< "name: "<<Constants::FILE_NAME;
    //for those who are unfamiliar with Qt, qDebug just prints out
    return a.exec();
}

编译时我得到了:

QCoreApplication :: applicationFilePath:请首先实例化QApplication对象

QCoreApplication::applicationFilePath: Please instantiate the QApplication object first

所以这里的问题很明显.在Constants.cpp中调用QApplication的静态函数时，Qt尚未安装QApplication.我需要以某种方式等待，直到在main.cpp中通过QApplication a(argc, argv);行

So problem here is obvious. When QApplication's static function is called in Constants.cpp QApplication is not installed by Qt yet. I need to somehow wait until QApplication a(argc, argv); line is passed in main.cpp

是否有可能，如果不能，您还有什么建议可以克服呢?

is it possible and if not what else could you suggest to overcome this?

谢谢

推荐答案

一种选择是从函数返回它，并将其保留在静态变量中.该函数将在首次调用该函数时初始化.

One option is to return it from a function, keeping it in a static variable. This will be initialised when the function is first called.

char const * const file_name()
{
    // Store the string, NOT the pointer to a temporary string's contents
    static std::string const file_name =
        QApplication::applicationFilePath().toStdString();
    return file_name.c_str();
}

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