2016年1月27日 · QString QString::fromUtf16(const ushort * unicode, int size = -1) const ushort* str = read_raw("hello.txt"); // assuming hello.txt is UTF16 encoded, and read_raw() reads bytes from file into memory and returns pointer to the first byte as const ushort* QString qstr = QString::fromUtf16(str);

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. E.g. QString myString("This is a string"); QStringRef subString(&myString, 5, 2); // subString contains "is"

2015年11月9日 · One drawback though: QString::arg() doesn't handle std::string. You will need to call: QString::fromStdString() on your std::string to make it into a QString before passing it to QString::arg(). Try to separate the classes that use QString from the classes that use std::string. Or if you can, switch to QString altogether.

@Vitali not correct. "The destructor for the QByteArray may be called before the constructor of the STL string" is not correct statement: Quoting the standard: 12.2.3 Temporary objects are destroyed as the last step in evaluating the full-expression (1.9) that (lexically) contains the point where they were created.

The idiomatic way to create an empty QString is using its default constructor, i.e. QString(). QString() creates a string for which both isEmpty() and isNull() return true. A QString created using the literal "" is empty (isEmpty() returns true) but not null (isNull() returns false). Both have a size()/length() of 0.

2014年9月14日 · Note that QString::number(0) is decidedly not null - it creates a QString with the value "0". You could also initialize the QString with a NULL pointer, but I wouldn't recommend it unless you're passing a pointer regardless of whether it's NULL or not (i.e., it could sometimes point to a C string) since it's unnecessary.

2020年8月29日 · I'm debugging a program using QString. I added printf to show contents of QString but it only shows 1st letter. Code is as below. fprintf is what I added. QString profilePath = mltPath; fpr...

2012年9月6日 · Given your path as a QString s. info = QFileInfo(s) // Get the name of the file without the extension base_name = info.baseName() // Add a ".avi" extension video_file ...

2011年11月9日 · You can also use the QString::arg() overload which take a field width parameter. The field width value is the total number of desired characters, not the padding size. The field width value is the total number of desired characters, not the padding size.

2017年12月28日 · QString is an interesting string class able to manipulate with both statically and dynamically allocated character strings. The dynamic allocation is more expensive in both code size and performance terms but more flexible and usually practical.