diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/qt3support/tools/q3cstring.cpp | 32 |
1 files changed, 27 insertions, 5 deletions
diff --git a/src/qt3support/tools/q3cstring.cpp b/src/qt3support/tools/q3cstring.cpp index 39f1c43..b33b9b6 100644 --- a/src/qt3support/tools/q3cstring.cpp +++ b/src/qt3support/tools/q3cstring.cpp @@ -77,11 +77,23 @@ QT_BEGIN_NAMESPACE and '\0' (NUL byte) terminated; otherwise the results are undefined. - A Q3CString that has not been assigned to anything is \e null, i.e. - both the length and the data pointer is 0. A Q3CString that - references the empty string ("", a single '\0' char) is \e empty. - Both null and empty Q3CStrings are legal parameters to the methods. - Assigning \c{const char *} 0 to Q3CString produces a null Q3CString. + A default constructed Q3CString is \e null, i.e. both the length + and the data pointer are 0 and isNull() returns true. + + \note However, if you ask for the data pointer of a null Q3CString + by calling data(), then because the internal representation of the + null Q3CString is shared, it will be detached and replaced with a + non-shared, empty representation, a non-null data pointer will be + returned, and subsequent calls to isNull() will return false. But + if you ask for the data pointer of a null Q3CString by calling + constData(), the shared internal representation is not detached, a + null data pointer is returned, and subsequent calls to isNull() + will continue to return true. + + A Q3CString that references the empty string ("", a single '\0' + char) is \e empty, i.e. isEmpty() returns true. Both null and + empty Q3CStrings are legal parameters to the methods. Assigning + \c{const char *} 0 to Q3CString produces a null Q3CString. The length() function returns the length of the string; resize() resizes the string and truncate() truncates the string. A string @@ -321,6 +333,16 @@ QT_BEGIN_NAMESPACE Returns true if the string is null, i.e. if data() == 0; otherwise returns false. A null string is also an empty string. + \note If you ask for the data pointer of a null Q3CString by + calling data(), then because the internal representation of the + null Q3CString is shared, it will be detached and replaced with a + non-shared, empty representation, a non-null data pointer will be + returned, and subsequent calls to isNull() will return false. But + if you ask for the data pointer of a null Q3CString by calling + constData(), the shared internal representation is not detached, a + null data pointer is returned, and subsequent calls to isNull() + will continue to return true. + Example: \snippet doc/src/snippets/code/src.qt3support.tools.q3cstring.cpp 1 |