Qt: QString::isEmpty()与QString::isNull()区别

Qt: QString::isEmpty()与QString::isNull()

bool QString::isEmpty () const

Returns true if the string has no characters; otherwise returns false.

Example:

QString().isEmpty(); // returns true
QString("").isEmpty(); // returns true
QString("x").isEmpty(); // returns false
QString("abc").isEmpty(); // returns false
See also size().

bool QString::isNull () const

Returns true if this string is null; otherwise returns false.

Example:

QString().isNull(); // returns true
QString("").isNull(); // returns false
QString("abc").isNull(); // returns false
Qt makes a distinction between null strings and empty strings for historical reasons. For most applications, what matters is whether or not a string contains any data, and this can be determined using the isEmpty() function.