逛奔的蝸牛

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.