How do you find the substring of QString?

2 Answers. If you do not need to modify the substring, then you can use QStringRef . The QStringRef class is a read only wrapper around an existing QString that references a substring within the existing string. This gives much better performance than creating a new QString object to contain the sub-string.

How do you find the length of a QString?

You need to use ::toUtf8() and append it to a QByteArray. Then you can get the length using . size().

What is QDebug in Qt?

The QDebug class provides an output stream for debugging information. QDebug is used whenever the developer needs to write out debugging or tracing information to a device, file, string or console.

How do I print QString?

You can do it using one of the following ways:

  1. QString someString = “Foo bar”;
  2. // Include for this.
  3. qDebug() << someString;
  4. std::cout << someString. toStdString();
  5. printf(someString. toStdString(). c_str());

How to search and replace a substring in Qt?

I’m looking for a way to replace any sub-string present in a QString object that is included in a hard-coded list of strings which include dozens of entries. Right now I’m passing QString::replace a QRegularExpression that covers all matching strings.

When to return the whole string in QString?

QString QString:: left (int n) const. Returns a substring that contains the n leftmost characters of the string. The entire string is returned if n is greater than or equal to size(), or less than zero.

How to find all occurrences of a substring in a QString?

If you want to find all occurrences of a particular character or substring in a QString, use the indexOf() or lastIndexOf() functions. The former searches forward starting from a given index position, the latter searches backward. Both return the index position of the character or substring if they find it; otherwise, they return -1.

How to find the index of a string in QString?

int QString:: indexOf (const QRegularExpression &re, int from = 0) const. This function overloads indexOf(). Returns the index position of the first match of the regular expression re in the string, searching forward from index position from. Returns -1 if re didn’t match anywhere. Example: