Posting on facebook wall from Qt

Recently I was working on upgrade of my application. As a part of upgrade I decided to allow user to post their game score to facebook wall.

I had done similar work for iPhone, here is link. But never from Qt.

I am sharing my experience here, in hope it will help someone.

To be able to post on wall first you need to create facebook application. You can do the from here.

After creating application, you will get application id. We need this application id for authorization.

We need to use following url for authorization.

In below request client_id is your facebook application id, score is required permission to call facebook graph API. for posting on user's wall read_stream and publish_stream is enough. Here is full list of permission.

https://www.facebook.com/dialog/oauth?
client_id=YOUR_APPP_ID&
redirect_uri=https://www.facebook.com/connect/login_success.html&
response_type=token&scope=read_stream,publish_stream 

Above url will offer user a login dialog and user needs to enter user name and password. if process is successful then we will get access token. I used QWebView for presenting dialog to user.

You can also use "https://m.facebook.com/dialog/oauth" for mobile version of login dialog.

Following is my Qt Code.

void FacebookHelper::login( const QString& scope ){

    QUrl url("https://www.facebook.com/dialog/oauth");
    url.addQueryItem("client_id",mAppId);
    url.addQueryItem("redirect_uri",
        "https://www.facebook.com/connect/login_success.html");
    url.addQueryItem("response_type","token");
    url.addQueryItem("scope",scope);

    //view = new QWebView();
    view->load( url );
    view->show();
    connect(view,SIGNAL(loadFinished(bool)),this,SLOT(loginResponse(bool)));
}

void FacebookHelper::loginResponse( bool status ){
    QUrl url= view->url();
    QString strUrl = url.toString();

    int sIndex = strUrl.indexOf("access_token=");
    int eIndex = strUrl.indexOf("&expires_in");
    if( sIndex != -1 && eIndex != -1 ){
        mAccessToken= strUrl.mid(sIndex, eIndex - sIndex);
        mAccessToken = mAccessToken.remove("access_token=");
        emit authStatus( mAccessToken);
    }
}

Access token will come as part of re directional url, like following.

http://YOUR_URL#access_token=166942940015970%7C2.sa0&expires_in=64090

Now we have access token, Using this token we can submit post to facebook wall.
You can use following curl request to test your access token and post a message to your facebook wall.

If you see post you your wall then authorization process is successful. Here https://graph.facebook.com/me/feed, url is used to post message on logged in user's wall. If you want to post message on friends post then you need to replace me with that user's id.

 curl -F 'access_token=ACCESS_TOKEN' \
     -F 'picture=URL OF SOME PICTURE' \
     -F 'caption=TITLE OF POST' \
     -F 'description=DETAILS OF POST' \
     -F 'name=NAME OF POST' \
     https://graph.facebook.com/me/feed

Following is my Qt code for sending message to user's wall.

....

        QMap data;
        data["access_token"] = mAccessToken;
        data["name"] = "Test ";
        data["caption"] = "Testing graph api";
        data["description"] = "Testing description field";
        data["picture"] = "URL";
        setMessage(data);
......

void FacebookHelper::setMessage( QMap<qstring,qstring>& post) {

    QString postData;
    foreach( QString key, post.keys()) {
        postData.append(key +"=" +post[key]+"&");
    }

    QNetworkRequest request(QUrl("https://graph.facebook.com/me/feed");
    mCurrentRequest  = mNetManager.post(request,postData.toAscii());
    connect(mCurrentRequest,SIGNAL(finished()),this,SLOT(messageResponse()));
}

Thant's all, Hope you liked it.