QString, remove labels and content? - c++

message.Text() is a QString.
I want to remove some text.
The text can be:
Normal: "This is a text"
With a label: "<label1>something</label1>This is a text"
First, I find if the text has the label:
!message.Text().contains("<label1>", Qt::CaseInsensitive))
So, if it has, I want to remove the first part, to have a normal text "This is a text".
I tried this:
first=message.Text().indexOf("<label1>");
last=message.Text().lastIndexOf("</label1>");
message.Text().remove(first,last);
But I got Compiler Error C2663.
I also know that the message.Text().remove(QChar('<label1'), Qt::CaseInsensitive); is another way to do it. But in my case, the part between the label is unkwnow.
It can be <label1>something</label1> or <label1>oisdioadj</label> or <label1>7</label1>....
Any idea?
Regards.

Try the following:
#include <iostream>
using std::cout; using std::endl;
#include <QString>
int main()
{
QString message = "<label1>something</label1>This is a test";
const QString labelClose = "</label1>";
const int labelCloseSize = labelClose.size();
cout << "message: " << qPrintable(message) << endl;
const int closePosition = message.lastIndexOf(labelClose);
QString justText = message.remove(0, closePosition + labelCloseSize);
cout << "just text: " << qPrintable(justText) << endl;
}

My advice here: keep things simple in your code, it will help making things simple in your head.
It seems what you want to achieve is more related to strings, than to label.
I suggest you get the text from your label, then work on it independently, then associate it back to your label:
QString text = message.text();
/* Do whatever you need to do here with text */
message.setText(text);
Also, the error you're having is probably due to the fact that you try to modify directly message.text() which is a const reference: obviously you can't modify something that is const.
I believe what you try to achieve can be done using QString::replace(). You'll have to use regular expressions for that, so if you're not familiar with it, it might be difficult.

Related

How do I find character in string and after that I extract the rest of string in C++

So my problem is next:
I have youtube link entered as input, and I should print youtubeID as output.
So, perhaps I have this link: https://www.youtube.com/watch?v=szyKv63JB3s , I should print this "szyKv63JB3s", so I came to conclusion that I need to find that " = " in user inputed string and I should look to make new string called "ytID" or "result" and store youtubeID from the moment I find that " = " characther.
So I really don't have idea how should it be done...
I mean I should go through string with for loop I guess, and after that I should store the part which will be called youtubeID, and I have problem there because I don't know how long is that link, I mean how much characthers it have, so I cannot really use for or while loops...
P.S This is not HOMEWORK, I just want to practice. :)
you should give a look at this post :
Removing everything after character (and also character)
A solution could be as simple as :
theString.substr( theString.find('=') ) ;
Just search for the character = as you mentioned in the question:
#include <iostream>
#include <string_view>
std::string_view extractYoutubeId(std::string_view const link) {
auto const off = link.find('=');
if (off == std::string_view::npos)
return std::string_view{};
return link.substr(off + 1);
}
int main() {
auto const& link = "https://www.youtube.com/watch?v=dQw4w9WgXcQ";
std::cout << extractYoutubeId(link);
}
Output: dQw4w9WgXcQ

Error in JSON string creation with / operator using jsoncpp library

I am using JSONcpp library and facing problem to create json which contains / operator (like date : 02/12/2015). Below is my code:
JSONNODE *n = json_new(JSON_NODE);
json_push_back(n, json_new_a("String Node", "02/05/2015"));
json_char *jc = json_write_formatted(n);
printf("%s\n", jc);
json_free(jc);
json_delete(n);
Output :
{
"String Node":"02\/05\/2015"
}
Check here "\/" in date, we want only "/" in date, so my expected output should look like this:
Expected output:
{
"String Node":"02/05/2015"
}
How to get rid of it? We are using inbuilt library function and we can not modify library.
According to this example
The json_new_a method will escape your string values when you go to
write the final string.
The additional backslashes you are facing in the output are the result of adding escape characters. This is actually a good thing as it prevents both accidental and intentional errors.
I suppose the easies option for you would be to replace all \/ occurrences in output string with single /. I wrote a simple program to do so:
#include <iostream>
#include <string>
#include <boost/algorithm/string/replace.hpp>
using namespace std;
int main()
{
//Here's the "json_char *jc" from your code
const char* jc = "02\\/05\\/2015";
//Replacing code
string str(jc);
boost::replace_all(str, "\\/", "/");
//Show result
cout << "Old output: " << jc << endl;
cout << "New output: " << str << endl;
}
Live demo
BTW: libJSON is not really a C++ library - it's much more C-style which involves many low-level operations and is more complicated and obfuscated than more C++ish libraries. If you'd like to try, there is a nice list of C++ JSON libs here.

How to print string literal and QString with qDebug?

Is there any easy way to get the following work? I mean is there any helper class in Qt which prepares the string for qDebug?
QString s = "value";
qDebug("abc" + s + "def");
You can use the following:
qDebug().nospace() << "abc" << qPrintable(s) << "def";
The nospace() is to avoid printing out spaces after every argument (which is default for qDebug()).
No really easy way I am aware of. You can do:
QByteArray s = "value";
qDebug("abc" + s + "def");
or
QString s = "value";
qDebug("abc" + s.toLatin1() + "def");
According to Qt Core 5.6 documentation you should use qUtf8Printable() from <QtGlobal> header to print QString with qDebug.
You should do as follows:
QString s = "some text";
qDebug("%s", qUtf8Printable(s));
or shorter:
QString s = "some text";
qDebug(qUtf8Printable(s));
See:
http://doc.qt.io/qt-5/qtglobal.html#qPrintable
http://doc.qt.io/qt-5/qtglobal.html#qUtf8Printable
Option 1: Use qDebug's default mode of a C-string format and variable argument list (like printf):
qDebug("abc%sdef", s.toLatin1().constData());
Option 2: Use the C++ version with overloaded << operator:
#include <QtDebug>
qDebug().nospace() << "abc" << qPrintable(s) << "def";
Reference: https://qt-project.org/doc/qt-5-snapshot/qtglobal.html#qDebug
Just rewrite your code like this:
QString s = "value";
qDebug() << "abc" << s << "def";
I know this question is a bit old, but it appears nearly on top when searching for it in the web. One can overload the operator for qDebug (more specific for QDebug) to make it accept std::strings like this:
inline QDebug operator<<(QDebug dbg, const std::string& str)
{
dbg.nospace() << QString::fromStdString(str);
return dbg.space();
}
This thing is for years in all of my projects, I nearly forget it is still not there by default.
After that, usage of << for qDebug() is a lot more usable imho. You can even mix QString and std::string. Some additional(but not really intended) feature is, that you sometimes can throw in integers or other types that allow implicit conversion to std::string .

C++ boost/regex regex_search

Consider the following string content:
string content = "{'name':'Fantastic gloves','description':'Theese gloves will fit any time period.','current':{'trend':'high','price':'47.1000'}";
I have never used regex_search and I have been searching around for ways to use it - I still do not quite get it. From that random string (it's from an API) how could I grab two things:
1) the price - in this example it is 47.1000
2) the name - in this example Fantastic gloves
From what I have read, regex_search would be the best approach here. I plan on using the price as an integer value, I will use regex_replace in order to remove the "." from the string before converting it. I have only used regex_replace and I found it easy to work with, I don't know why I am struggling so much with regex_search.
Keynotes:
Content is contained inside ' '
Content id and value is separated by :
Conent/value are separated by ,
Value of id's name and price will vary.
My first though was to locate for instance price and then move 3 characters ahead (':') and gather everything until the next ' - however I am not sure if I am completely off-track here or not.
Any help is appreciated.
boost::regex would not be needed. Regular expressions are used for more general pattern matching, whereas your example is very specific. One way to handle your problem is to break the string up into individual tokens. Here is an example using boost::tokenizer:
#include <iostream>
#include <string>
#include <boost/tokenizer.hpp>
#include <map>
int main()
{
std::map<std::string, std::string> m;
std::string content = "{'name':'Fantastic gloves','description':'Theese gloves will fit any time period.','current':{'trend':'high','price':'47.1000'}";
boost::char_separator<char> sep("{},':");
boost::tokenizer<boost::char_separator<char>> tokenizer(content, sep);
std::string id;
for (auto tok = tokenizer.begin(); tok != tokenizer.end(); ++tok)
{
// Since "current" is a special case I added code to handle that
if (*tok != "current")
{
id = *tok++;
m[id] = *tok;
}
else
{
id = *++tok;
m[id] = *++tok; // trend
id = *++tok;
m[id] = *++tok; // price
}
}
std::cout << "Name: " << m["name"] << std::endl;
std::cout << "Price: " << m["price"] << std::endl;
}
Link to live code.
As the string you are attempting to parse appears to be JSON (JavaScript Object Notation), consider using a specialized JSON parser.
You can find a comprehensive list of JSON parsers in many languages including C++ at http://json.org/. Also, I found a discussion on the merits of several JSON parsers for C++ in response to this SO question.

How do I insert a variable result into a string in C++

I just started learning C++ in Qt and I was wondering how can I put a variables result in a string? I'm trying to use this for a simple application where someone puts their name in a text field then presses a button and it displays there name in a sentence. I know in objective-c it would be like,
NSString *name = [NSString stringWithFormatting:#"Hello, %#", [nameField stringValue]];
[nameField setStringValue:name];
How would I go about doing something like this with C++? Thanks for the help
I assume we're talking about Qt's QString class here. In this case, you can use the arg method:
int i; // current file's number
long total; // number of files to process
QString fileName; // current file's name
QString status = QString("Processing file %1 of %2: %3")
.arg(i).arg(total).arg(fileName);
See the QString documentation for more details about the many overloads of the arg method.
You donĀ“t mention what type your string is. If you are using the standard library then it would be something along the lines of
std::string name = "Hello, " + nameField;
That works for concatenating strings, if you want to insert other complex types you can use a stringstream like this:
std::ostringstream stream;
stream << "Hello, " << nameField;
stream << ", here is an int " << 7;
std::string text = stream.str();
Qt probably has its own string types, which should work in a similar fashion.
I would use a stringstream but I'm not 100% sure how that fits into your NSString case...
stringstream ss (stringstream::in);
ss << "hello my name is " << nameField;
I think QString has some nifty helpers that might do the same thing...
QString hello("hello ");
QString message = hello % nameField;
You could use QString::sprintf. I haven't found a good example of it's use yet, though. (If someone else finds one, feel free to edit it in to this answer).
You might be interested in seeing information about the difference between QString::sprintf and QString::arg.