How can I get things from website

[J.Hilk]

@victor-wang
My bad, QNetworkReply::error is an overloaded function.

use this:

connect(networkReply, static_cast<void(QNetworkReply::*)(QNetworkReply::NetworkError)>(&QNetworkReply::error),
    [=](QNetworkReply::NetworkError code){ qDebug() << code; });

taken from the docu

[JKSH]

@J.Hilk said in How can I get things from website:

connect(networkReply, static_cast<void(QNetworkReply::*)(QNetworkReply::NetworkError)>(&QNetworkReply::error),
    [=](QNetworkReply::NetworkError code){ qDebug() << code; });

taken from the docu

In Qt 5.7 onwards, you can also use qOverload() (with C++14) or QOverload (C++11), instead of the longer static_cast: http://doc.qt.io/qt-5/qtglobal.html#qOverload

connect(networkReply, qOverload<QNetworkReply::NetworkError>(&QNetworkReply::error),
    [=](QNetworkReply::NetworkError code) { qDebug() << code; });

[victor wang]

@JKSH @J-Hilk
I'm using Qt5.5 so i can't use qOverload on my Qt version.
I had changed it but it still got error.
This is my code here

And this is the error that i got here

It's the same error shows no matching function for call.
What else should i do ?

[JKSH]

@victor-wang said in How can I get things from website:

And this is the error that i got here

You have a warning message: "lambda expressions only available with -std=c++11 or -std=gnu++11"

That means haven't enabled C++11.

Add this line to your *.pro file to enable it: CONFIG += C++11

[victor wang]

@JKSH
I can compiled it successfully.
But i don't know what this is doing ?
I still can't get any information from my Url.

This is my code here

And this is what i got here

I didn't get any error back but also didn't get what i want back either.

This is the Url i want to get http://192.168.100.59/PLMS/TestCheck.asp?LSN=201503003009&EmpId=we9999&CPID=OS&CPKey=95Z0000000AF

I should get a file or get a respond that said ok.

[JKSH]

Please post your code as text, not pictures. Text is much easier to read and search.

Anyway, what is inside your replyFinished() function?

[victor wang]

@JKSH

void MainWindow::replyFinished(QNetworkReply *reply)
{
qDebug("connect content");
QTextCodec *codec=QTextCodec::codecForLocale();
int connect_url=reply -> attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();
qDebug()<<connect_url;
qDebug("here");

}

Sorry, i'm using Qt via Xming and i can't just copy the code to my local computer.
I have to type myself.

For the picture i just gave you.
"connect_url" will print the number 200 out to make sure the Url is connecting successfully.

[JKSH]

@victor-wang said in How can I get things from website:

"connect_url" will print the number 200 out to make sure the Url is connecting successfully.

Yes, 200 means "HTTP OK": http://www.restapitutorial.com/httpstatuscodes.html

Your code is connecting to the server OK.

void MainWindow::replyFinished(QNetworkReply *reply)
{
qDebug("connect content");
QTextCodec *codec=QTextCodec::codecForLocale();
int connect_url=reply -> attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();
qDebug()<<connect_url;
qDebug("here");

}

You need to read the data from the QNetworkReply. Call reply->readAll() to get the data.

Also, remember to delete your QNetworkReply after you have finished, or else you will have a memory leak. See the QNetworkReply documentation: http://doc.qt.io/qt-5/qnetworkreply.html

@victor-wang said in [How can I get things from website](/topic/77075/how-can-i-get-things-from-

I should get a file

As I said above, you must call reply->readAll() to get the data. Then, write the data into a file using a QFile.

[victor wang]

@JKSH
you mean i have to add this after the connect function?

qDebug()<<reply->readAll();
reply->deleteLater();

Is that readAll will print the information out?
Or i have to using qDebug to print it out?

[JKSH]

@victor-wang said in How can I get things from website:

@JKSH
you mean i have to add this after the connect function?

qDebug()<<reply->readAll();
reply->deleteLater();

I mean you have to add this inside your replyFinished() slot.

Are you familiar with asynchronous programming? Networking is asynchronous. When you call QNetworkAccessManager::get(), it starts downloading. However, it doesn't wait for the download to finish. Instead, QNetworkAccessManager and QNetworkReply WILL emit the finished() signal when the download finishes. So, you can read the downloaded data from inside the connected slot.

Is that readAll will print the information out?
Or i have to using qDebug to print it out?

readAll() gives you the data in a QByteArray. It doesn't print anything. Do you know how to use QByteArray?

qDebug prints to the console.

[victor wang]

@JKSH

I am not quite sure that i'm using the right way.
I write this code into replyFinished();

QByteArray output;
output = reply -> readAll();
qDebug()<<output;
reply->deleteLater();

Am i right?
Sorry i'm new in Qt please be patient to me:(

[JKSH]

@victor-wang said in How can I get things from website:

I write this code into replyFinished();

QByteArray output;
output = reply -> readAll();
qDebug()<<output;
reply->deleteLater();

Am i right?

Yes, that is right :)

Now, you can save output into a file, using QFile.

Sorry i'm new in Qt please be patient to me:(

No problem! We are happy to help beginners. I think you are learning well.

[victor wang]

@JKSH
I this function will show the content out?

qDebug()<<output;

If it is why it showed NULL on the console. here
I thought it will print the Url information which i had just gave you "Updated ok!".

[victor wang]

@victor-wang

I add this after connect instead of replyFinished slot.

file.setFileName("/home/check.txt");
if(!file.exist)qDebug("not exist");
if(!file.open(QIODevice::WriteOny | QIODevice::Text))qDebug("not write success");
stream.setDevice(&file);
stream<<out;
file.close;

But when i went to cat the check.txt there is nothing in the file.

And i add this in my replyFinished slot.

out=reply->readAll();
qDebug()<<out;
reply->deleteLater();

The "QByteArray out" i had declared it in the mainwidow.h for global type.
Did i need to put in the private place or the public place in the mainwindow.h?

Why i still didn't see anything in my file?

[JKSH]

@victor-wang said in How can I get things from website:

I this function will show the content out?

qDebug()<<output;

Yes.

The "QByteArray out" i had declared it in the mainwidow.h for global type.
Did i need to put in the private place or the public place in the mainwindow.h?

No, no need.

@victor-wang said in How can I get things from website:

I add this after connect instead of replyFinished slot.

That definitely won't work, because you haven't received the data yet.

Remember, networking is asynchronous. You can only read the data after the finished() signal is emitted.

If it is why it showed NULL on the console. here
I thought it will print the Url information which i had just gave you "Updated ok!".
...
Why i still didn't see anything in my file?

This is where you need to start debugging and testing.

1. What do you get when you type your URL into your browser?
2. What happens when you change the URL to http://lists.qt-project.org/mailman/listinfo ?
3. Is your QNetworkRequest constructed correctly?
4. Is your device on the same subnet as the server?

[victor wang]

@JKSH
Is that you mean i have to add this QFile function in the replyFinisheed() slot?
Or i have to do it when the finished signal is up?
If it is how can i judge the signal and where do i have to add the function in?

For the first of debugging and testing.
I will get this on my browser. here

For the second one, i'm not quite sure what does that mean.

For third one, what does"QNetworkRequest constructly correctly"mean?
I thought i am using the library that Qt have already constructed.

For forth one, I'm sure i am on the same subnet because i can send this commend to my console

wget http://192.168.100.59/PLMS/TestCheck.asp?LSN=201503003009&EmpId=we9999&CPID=OS&CPKey=95Z0000000AF

And i will get the file and the content will show "updated ok".

[victor wang]

@JKSH
I had add qDebug() function in replyFinished() slot.
Here is my code.

According to what you said it will print something out if i am in the same subnet.
And i'm sure that i am in the same subnet but why it still print NULL out like this?

According to the picture i gave you, i assume that it will return "Updated ok!" back to me.

[jsulm]

@victor-wang said in How can I get things from website:

Or i have to do it when the finished signal is up?

@JKSH already said several times that you have to do it in the slot connected to the finished() signal. So, yes do it in when you get finished() signal.
To your code: you call readAll twice - that is probably the reason why qDebug() << out; prints nothing. You should call readAll only once and then print the data.

[victor wang]

@jsulm
That mean i have to add QFile function into replyFinished() SLOT right?

ReadAll function actually it call twice by itself and i don't know why it will happened.
I'm sure that i just call one time for the ReadAll function.
This is my code here.

But when I add it into replyFinished() slot, it cannot connect to server.
The connect_url will return 0 for the second time to me like this.
What can i do?

[jsulm]

@victor-wang YES
"ReadAll function actually it call twice by itself" - how can a function call itself?
You do it twice, please check your own code again. First time: line 1999, second time line 2013.