Issue in downloading with QNetworkAccessManager

[bikonja]

Hi, i'm making an currency converter app.
I go online, download a html and save it into a txt file, which i parse afterwards for the exchange rates.

.h

#ifndef DOWNLOADER_H
#define DOWNLOADER_H
 
#include <QObject>
#include <QNetworkAccessManager>
#include <QNetworkRequest>
#include <QNetworkReply>
#include <QUrl>
#include <QFile>
#include <QDebug>
#include <QMessageBox>
#include <string>
#include <Windows.h>
#include <qstring.h>
 
 
class downloader : public QObject
{
    Q_OBJECT
public:
    explicit downloader(QObject *parent = 0);
 
    void Do_download();
 
public slots:
    void replyFinished (QNetworkReply *reply);
 
private:
    QNetworkAccessManager *manager;
 
};

#ifndef DOWNLOADER_H
#define DOWNLOADER_H

#include <QObject>
#include <QNetworkAccessManager>
#include <QNetworkRequest>
#include <QNetworkReply>
#include <QUrl>
#include <QFile>
#include <QDebug>
#include <QMessageBox>
#include <string>
#include <Windows.h>
#include <qstring.h>


class downloader : public QObject
{
    Q_OBJECT
public:
    explicit downloader(QObject *parent = 0);

    void Do_download();

public slots:
    void replyFinished (QNetworkReply *reply);

private:
    QNetworkAccessManager *manager;

};

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.cpp

#include "downloader.h"
#include "strings.h"
#include <string>
#include <Windows.h>
 
downloader::downloader(QObject *parent) :
    QObject(parent)
{
 
}
 
 
void downloader::Do_download()
{
    manager = new QNetworkAccessManager(this);
 
    connect(manager, SIGNAL(finished(QNetworkReply*)),
            this,SLOT(replyFinished(QNetworkReply*)));
 
            manager->get(QNetworkRequest(QUrl("http://www.hnb.hr/tecajn/hvazeca.htm")));
}
 
void downloader::replyFinished(QNetworkReply *reply)
{
    if(reply->error())
    {
        QMessageBox msgBox;
		msgBox.setText(strings::msgBoxDownReplyError);
        msgBox.exec();
    }
    else
    {
 
		QFile *file = new QFile("C:/Qt/test/downloaded.txt");
        QByteArray data = reply->readAll();
 
        if(file->open(QIODevice::ReadWrite | QIODevice::Truncate | QIODevice::Text))
            {
            file->write(data);
            file->flush();
            file->close();
        }
        delete file;
 
    }
    reply->deleteLater();
 
}

#include "downloader.h"
#include "strings.h"
#include <string>
#include <Windows.h>

downloader::downloader(QObject *parent) :
    QObject(parent)
{
	
}


void downloader::Do_download()
{
    manager = new QNetworkAccessManager(this);

    connect(manager, SIGNAL(finished(QNetworkReply*)),
            this,SLOT(replyFinished(QNetworkReply*)));

            manager->get(QNetworkRequest(QUrl("http://www.hnb.hr/tecajn/hvazeca.htm")));
}

void downloader::replyFinished(QNetworkReply *reply)
{
    if(reply->error())
    {
        QMessageBox msgBox;
		msgBox.setText(strings::msgBoxDownReplyError);
        msgBox.exec();
    }
    else
    {

		QFile *file = new QFile("C:/Qt/test/downloaded.txt");
        QByteArray data = reply->readAll();

        if(file->open(QIODevice::ReadWrite | QIODevice::Truncate | QIODevice::Text))
            {
            file->write(data);
            file->flush();
            file->close();
        }
        delete file;

    }
    reply->deleteLater();

}

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parser.h

#ifndef PARSER_H
#define PARSER_H
 
 
#include <QMessageBox>
#include <QStringList>
#include <string>
#include <sstream>
#include <stdlib.h>
#include <fstream>
#include <iostream>
#include <algorithm>
#include <string>
#include <Windows.h>
 
 
class parser 
 
{
 
public:
     explicit parser();
 
    QStringList currency_list;
	std::list<std::string> curr_list;
 
    void process_line(std::string line, std::map<std::string,double> &my_map, std::string curr_string);
    int read_line(std::map<std::string,double> &my_map);
 
    void init_list();
 
	std::string getExePathParser();
 
private:
 
};
 
#endif // PARSER_H

#ifndef PARSER_H
#define PARSER_H


#include <QMessageBox>
#include <QStringList>
#include <string>
#include <sstream>
#include <stdlib.h>
#include <fstream>
#include <iostream>
#include <algorithm>
#include <string>
#include <Windows.h>


class parser 

{
   
public:
     explicit parser();

    QStringList currency_list;
	std::list<std::string> curr_list;

    void process_line(std::string line, std::map<std::string,double> &my_map, std::string curr_string);
    int read_line(std::map<std::string,double> &my_map);

    void init_list();
   
	std::string getExePathParser();

private:

};

#endif // PARSER_H

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parser.cpp

#include "parser.h"
#include "calculator.h"
#include "strings.h"
#include <string>
 
parser::parser()   
{
        init_list();
 
}
void parser::process_line(std::string line, std::map<std::string,double> &my_map, std::string curr_string)
{
	double curr;
	std::string temp;
 
	temp = line.substr(52,8);
 
	std::replace(temp.begin(),temp.end(),',','.');
 
	curr = std::stod(temp,NULL);
 
	my_map.insert(std::make_pair(curr_string,curr));
 
}
 
 
int parser::read_line(std::map<std::string,double> &my_map)
{
 
	std::list<std::string>::iterator iter;
	std::string linija;
	std::ifstream file_("C:/Qt/test/downloaded.txt");
 
	if(file_.fail())
	{
		QMessageBox msgBox;
		msgBox.setText(strings::msgBoxOpeningError);
        msgBox.exec();
	}
 
	else if(file_.is_open())
	{
		while(std::getline(file_,linija))
		{
			for(iter=curr_list.begin(); iter != curr_list.end(); ++iter)
			{
			if(linija.find(*iter) != std::string::npos)
			process_line(linija, my_map, *iter);
			}
		}
		file_.close();
	}
 
    return 0;
}
 
 
 
void parser::init_list()
{
    currency_list << "HRK" << "CAD" << "CZK" << "DKK" << "HUF" 
		          << "JPY" << "NOK" << "SEK" << "CHF" << "GBP" 
			      << "USD" << "EUR" << "PLN" << "AUD";
	curr_list.push_back("HRK");
	curr_list.push_back("CAD");
	curr_list.push_back("CZK");
	curr_list.push_back("DKK");
	curr_list.push_back("HUF");
	curr_list.push_back("JPY");
	curr_list.push_back("NOK");
	curr_list.push_back("SEK");
	curr_list.push_back("CHF");
	curr_list.push_back("GBP");
	curr_list.push_back("USD");
	curr_list.push_back("EUR");
	curr_list.push_back("PLN");
	curr_list.push_back("AUD");
 
 
}

#include "parser.h"
#include "calculator.h"
#include "strings.h"
#include <string>

parser::parser()   
{
        init_list();

}
void parser::process_line(std::string line, std::map<std::string,double> &my_map, std::string curr_string)
{
	double curr;
	std::string temp;

	temp = line.substr(52,8);

	std::replace(temp.begin(),temp.end(),',','.');
	
	curr = std::stod(temp,NULL);

	my_map.insert(std::make_pair(curr_string,curr));
		
}


int parser::read_line(std::map<std::string,double> &my_map)
{

	std::list<std::string>::iterator iter;
	std::string linija;
	std::ifstream file_("C:/Qt/test/downloaded.txt");

	if(file_.fail())
	{
		QMessageBox msgBox;
		msgBox.setText(strings::msgBoxOpeningError);
        msgBox.exec();
	}

	else if(file_.is_open())
	{
		while(std::getline(file_,linija))
		{
			for(iter=curr_list.begin(); iter != curr_list.end(); ++iter)
			{
			if(linija.find(*iter) != std::string::npos)
			process_line(linija, my_map, *iter);
			}
		}
		file_.close();
	}

    return 0;
}



void parser::init_list()
{
    currency_list << "HRK" << "CAD" << "CZK" << "DKK" << "HUF" 
		          << "JPY" << "NOK" << "SEK" << "CHF" << "GBP" 
			      << "USD" << "EUR" << "PLN" << "AUD";
	curr_list.push_back("HRK");
	curr_list.push_back("CAD");
	curr_list.push_back("CZK");
	curr_list.push_back("DKK");
	curr_list.push_back("HUF");
	curr_list.push_back("JPY");
	curr_list.push_back("NOK");
	curr_list.push_back("SEK");
	curr_list.push_back("CHF");
	curr_list.push_back("GBP");
	curr_list.push_back("USD");
	curr_list.push_back("EUR");
	curr_list.push_back("PLN");
	curr_list.push_back("AUD");


}

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and my main

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
 
	std::map<std::string,double> currency_map;
 
 
    downloader d;
    d.Do_download();
 
 
	parser p;
    p.read_line(currency_map);
 
 
    MainWindow w(currency_map);
    w.show();
 
 
    return a.exec();
};

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

	std::map<std::string,double> currency_map;


    downloader d;
    d.Do_download();
    

	parser p;
    p.read_line(currency_map);
    

    MainWindow w(currency_map);
    w.show();
	

    return a.exec();
};

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It was working good, but then i changed the path for the .txt file i create.
And the first time i run the app, i get a msgBoxError from my parser class

if(file_.fail())
	{
		QMessageBox msgBox;
		msgBox.setText(strings::msgBoxOpeningError);
        msgBox.exec();
	}

if(file_.fail())
	{
		QMessageBox msgBox;
		msgBox.setText(strings::msgBoxOpeningError);
        msgBox.exec();
	}

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this part of code pops up.
then i shut it down. run the app again, and it's all working well.
so everytime i change the file path, the first running of the app wont work.
can someone help me out, and spot what's wrong here?

(i have to use basic c++ in some parts of the code, don't ask)

[anda_skoa]

You call Do_download() and immediately try to parse it.
Since downloading something is not instantanious and you write the file after the download finished, there is no file to parse when you attempt to.

I can recommend adding some qDebug() logging into the application when things like that happen, it would have told you that this is the sequence of how things currently happen.

Cheers,
_

[bikonja]

I can't seem to get this to work.

.h

#ifndef DOWNLOADER_H
#define DOWNLOADER_H
 
#include <QObject>
#include <QNetworkAccessManager>
#include <QNetworkRequest>
#include <QNetworkReply>
#include <QUrl>
#include <QFile>
#include <QDebug>
#include <QMessageBox>
#include <string>
#include <Windows.h>
#include <qstring.h>
 
class downloader : public QObject
{
    Q_OBJECT
public:
    explicit downloader(QObject *parent = 0);
 
    void Do_download();
 
	std::string getExePath();
 
	void Do_parse(bool download, QNetworkReply *reply);
 
public slots:
    void replyFinished (QNetworkReply *reply);
 
private:
    QNetworkAccessManager *manager;
	bool downloadSuccess;
 
};
 
#endif // DOWNLOADER_H

#ifndef DOWNLOADER_H
#define DOWNLOADER_H

#include <QObject>
#include <QNetworkAccessManager>
#include <QNetworkRequest>
#include <QNetworkReply>
#include <QUrl>
#include <QFile>
#include <QDebug>
#include <QMessageBox>
#include <string>
#include <Windows.h>
#include <qstring.h>

class downloader : public QObject
{
    Q_OBJECT
public:
    explicit downloader(QObject *parent = 0);

    void Do_download();

	std::string getExePath();

	void Do_parse(bool download, QNetworkReply *reply);

public slots:
    void replyFinished (QNetworkReply *reply);

private:
    QNetworkAccessManager *manager;
	bool downloadSuccess;

};

#endif // DOWNLOADER_H

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i added a bool variable, to check if download passed, and a Do_parse function to call afterwards.

.cpp

#include "downloader.h"
#include "strings.h"
#include <string>
#include <Windows.h>
 
downloader::downloader(QObject *parent) :
    QObject(parent)
{
	downloadSuccess = false;
}
 
 
void downloader::Do_download()
{
    manager = new QNetworkAccessManager(this);
 
    connect(manager, SIGNAL(finished(QNetworkReply*)),
            this,SLOT(replyFinished(QNetworkReply*)));
 
            manager->get(QNetworkRequest(QUrl("http://www.hnb.hr/tecajn/hvazeca.htm")));
 
	Do_parse(downloadSuccess, reply);   // this doesn't work
}
 
void downloader::replyFinished(QNetworkReply *reply)
{
 
    if(reply->error())
    {
        QMessageBox msgBox;
		msgBox.setText(strings::msgBoxDownReplyError);
        msgBox.exec();
		downloadSuccess = false;
    }
    else
    {
 
		downloadSuccess = true;
 
	}
}
 
void downloader::Do_parse(bool download, QNetworkReply *reply)
{
	 if(download==true)
{
		QFile *file = new QFile(strings::filePathQt);
        QByteArray data = reply->readAll();
 
        if(file->open(QIODevice::ReadWrite | QIODevice::Truncate | QIODevice::Text))
            {
            file->write(data);
            file->flush();
            file->close();
        }
        delete file;
 
    reply->deleteLater();
}
 
}

#include "downloader.h"
#include "strings.h"
#include <string>
#include <Windows.h>

downloader::downloader(QObject *parent) :
    QObject(parent)
{
	downloadSuccess = false;
}


void downloader::Do_download()
{
    manager = new QNetworkAccessManager(this);

    connect(manager, SIGNAL(finished(QNetworkReply*)),
            this,SLOT(replyFinished(QNetworkReply*)));

            manager->get(QNetworkRequest(QUrl("http://www.hnb.hr/tecajn/hvazeca.htm")));

	Do_parse(downloadSuccess, reply);   // this doesn't work
}

void downloader::replyFinished(QNetworkReply *reply)
{

    if(reply->error())
    {
        QMessageBox msgBox;
		msgBox.setText(strings::msgBoxDownReplyError);
        msgBox.exec();
		downloadSuccess = false;
    }
    else
    {
  
		downloadSuccess = true;

	}
}

void downloader::Do_parse(bool download, QNetworkReply *reply)
{
	 if(download==true)
{
		QFile *file = new QFile(strings::filePathQt);
        QByteArray data = reply->readAll();

        if(file->open(QIODevice::ReadWrite | QIODevice::Truncate | QIODevice::Text))
            {
            file->write(data);
            file->flush();
            file->close();
        }
        delete file;

    reply->deleteLater();
}

}

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I thought of something like this. but i guess i'm missing something about the reply thing.
Am i on the right track here?
Is it possible to send the reply into another function like i tried in my code?

[anda_skoa]

You schedule the download (QNAM::get()) and then call Do_parse, before the QNAM even had the chance to do anything.

replyFinished() is obviously a place where code gets executed after the download finished, so there is where you need to call Do_parse.
Not before the download happens.

Cheers,
_