我想创建一个我想在我的程序中使用的QSet<Tag>。Tag是我的自定义类。
当我构建代码时，我获得关于qHash过载的gcc错误:
Exercise.cpp.o
In file included from /opt/Qt/5.5/gcc_64/include/QtCore/qglobal.h:74:0,
from /opt/Qt/5.5/gcc_64/include/QtCore/qchar.h:37,
from /opt/Qt/5.5/gcc_64/include/QtCore/qstring.h:41,
from /opt/Qt/5.5/gcc_64/include/QtCore/QString:1,
from /src/wmathtest/LaTeXText.h:4,
from /src/wmathtest/Exercise.h:4,
from /src/wmathtest/Exercise.cpp:1:
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h: In instantiation of ‘uint qHash(const T&, uint) [with T = WMathTest::Tag; uint = unsigned int]’:
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:952:32: required from ‘QHash<Key, T>::Node** QHash<Key, T>::findNode(const Key&, uint*) const [with Key = WMathTest::Tag; T = QHashDummyValue; QHash<Key, T>::Node = QHashNode<WMathTest::Tag, QHashDummyValue>; uint = unsigned int]’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:808:36: required from ‘QHash<Key, T>::iterator QHash<Key, T>::insert(const Key&, const T&) [with Key = WMathTest::Tag; T = QHashDummyValue]’
/opt/Qt/5.5/gcc_64/include/QtCore/qset.h:188:94: required from ‘QSet<T>::iterator QSet<T>::insert(const T&) [with T = WMathTest::Tag]’
/src/wmathtest/Exercise.cpp:22:22: required from here
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:103:5: error: no matching function for call to ‘qHash(const WMathTest::Tag&)’
Q_DECL_NOEXCEPT_EXPR(noexcept(qHash(t)))
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:103:5: note: candidates are:
In file included from /opt/Qt/5.5/gcc_64/include/QtCore/qset.h:37:0,
from /opt/Qt/5.5/gcc_64/include/QtCore/QSet:1,
from /src/wmathtest/Tag.h:5,
from /src/wmathtest/Exercise.h:5,
from /src/wmathtest/Exercise.cpp:1:
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:65:52: note: constexpr uint qHash(char, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(char key, uint seed = 0) Q_DECL_NOTHROW { return uint(key) ^ seed; }
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:65:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘char’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:66:52: note: constexpr uint qHash(uchar, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(uchar key, uint seed = 0) Q_DECL_NOTHROW { return uint(key) ^ seed; }
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:66:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘uchar {aka unsigned char}’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:67:52: note: constexpr uint qHash(signed char, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(signed char key, uint seed = 0) Q_DECL_NOTHROW { return uint(key) ^ seed; }
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:67:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘signed char’
In file included from /opt/Qt/5.5/gcc_64/include/QtCore/qset.h:37:0,
from /opt/Qt/5.5/gcc_64/include/QtCore/QSet:1,
from /src/wmathtest/Tag.h:5,
from /src/wmathtest/Exercise.h:5,
from /src/wmathtest/Exercise.cpp:1:
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:68:52: note: constexpr uint qHash(ushort, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(ushort key, uint seed = 0) Q_DECL_NOTHROW { return uint(key) ^ seed; }
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:68:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘ushort {aka short unsigned int}’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:69:52: note: constexpr uint qHash(short int, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(short key, uint seed = 0) Q_DECL_NOTHROW { return uint(key) ^ seed; }
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:69:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘short int’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:70:52: note: constexpr uint qHash(uint, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(uint key, uint seed = 0) Q_DECL_NOTHROW { return key ^ seed; }
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:70:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘uint {aka unsigned int}’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:71:52: note: constexpr uint qHash(int, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(int key, uint seed = 0) Q_DECL_NOTHROW { return uint(key) ^ seed; }
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:71:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘int’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:72:52: note: constexpr uint qHash(ulong, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(ulong key, uint seed = 0) Q_DECL_NOTHROW
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:72:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘ulong {aka long unsigned int}’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:78:52: note: constexpr uint qHash(long int, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(long key, uint seed = 0) Q_DECL_NOTHROW { return qHash(ulong(key), seed); }
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:78:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘long int’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:79:52: note: constexpr uint qHash(quint64, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(quint64 key, uint seed = 0) Q_DECL_NOTHROW
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:79:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘quint64 {aka long long unsigned int}’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:83:52: note: constexpr uint qHash(qint64, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(qint64 key, uint seed = 0) Q_DECL_NOTHROW { return qHash(quint64(key), seed); }
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:83:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘qint64 {aka long long int}’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:84:42: note: uint qHash(float, uint)
Q_CORE_EXPORT Q_DECL_CONST_FUNCTION uint qHash(float key, uint seed = 0) Q_DECL_NOTHROW;
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:84:42: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘float’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:85:42: note: uint qHash(double, uint)
Q_CORE_EXPORT Q_DECL_CONST_FUNCTION uint qHash(double key, uint seed = 0) Q_DECL_NOTHROW;
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:85:42: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘double’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:87:42: note: uint qHash(long double, uint)
Q_CORE_EXPORT Q_DECL_CONST_FUNCTION uint qHash(long double key, uint seed = 0) Q_DECL_NOTHROW;
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:87:42: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘long double’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:89:52: note: constexpr uint qHash(QChar, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(const QChar key, uint seed = 0) Q_DECL_NOTHROW { return qHash(key.unicode(), seed); }
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:89:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘QChar’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:90:41: note: uint qHash(const QByteArray&, uint)
Q_CORE_EXPORT Q_DECL_PURE_FUNCTION uint qHash(const QByteArray &key, uint seed = 0) Q_DECL_NOTHROW;
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:90:41: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘const QByteArray&’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:91:41: note: uint qHash(const QString&, uint)
Q_CORE_EXPORT Q_DECL_PURE_FUNCTION uint qHash(const QString &key, uint seed = 0) Q_DECL_NOTHROW;
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:91:41: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘const QString&’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:92:41: note: uint qHash(const QStringRef&, uint)
Q_CORE_EXPORT Q_DECL_PURE_FUNCTION uint qHash(const QStringRef &key, uint seed = 0) Q_DECL_NOTHROW;
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:92:41: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘const QStringRef&’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:93:41: note: uint qHash(const QBitArray&, uint)
Q_CORE_EXPORT Q_DECL_PURE_FUNCTION uint qHash(const QBitArray &key, uint seed = 0) Q_DECL_NOTHROW;
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:93:41: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘const QBitArray&’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:94:41: note: uint qHash(QLatin1String, uint)
Q_CORE_EXPORT Q_DECL_PURE_FUNCTION uint qHash(QLatin1String key, uint seed = 0) Q_DECL_NOTHROW;
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:94:41: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘QLatin1String’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:98:32: note: template<class T> uint qHash(const T*, uint)
template <class T> inline uint qHash(const T *key, uint seed = 0) Q_DECL_NOTHROW
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:98:32: note: template argument deduction/substitution failed:
In file included from /opt/Qt/5.5/gcc_64/include/QtCore/qglobal.h:74:0,
from /opt/Qt/5.5/gcc_64/include/QtCore/qchar.h:37,
from /opt/Qt/5.5/gcc_64/include/QtCore/qstring.h:41,
from /opt/Qt/5.5/gcc_64/include/QtCore/QString:1,
from /src/wmathtest/LaTeXText.h:4,
from /src/wmathtest/Exercise.h:4,
from /src/wmathtest/Exercise.cpp:1:
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:103:5: note: mismatched types ‘const T*’ and ‘WMathTest::Tag’
Q_DECL_NOEXCEPT_EXPR(noexcept(qHash(t)))
^
src/wmathtest/CMakeFiles/wmathtest.dir/build.make:146: recipe for target 'src/wmathtest/CMakeFiles/wmathtest.dir/Exercise.cpp.o' failed
make[2]: *** [src/wmathtest/CMakeFiles/wmathtest.dir/Exercise.cpp.o] Error 1
CMakeFiles/Makefile2:160: recipe for target 'src/wmathtest/CMakeFiles/wmathtest.dir/all' failed
make[1]: *** [src/wmathtest/CMakeFiles/wmathtest.dir/all] Error 2
Makefile:76: recipe for target 'all' failed
Exercise.cpp.o
In file included from /opt/Qt/5.5/gcc_64/include/QtCore/qglobal.h:74:0,
from /opt/Qt/5.5/gcc_64/include/QtCore/qchar.h:37,
from /opt/Qt/5.5/gcc_64/include/QtCore/qstring.h:41,
from /opt/Qt/5.5/gcc_64/include/QtCore/QString:1,
from /wmathtest/LaTeXText.h:4,
from /src/wmathtest/Exercise.h:4,
from /wmathtest/Exercise.cpp:1:
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h: In instantiation of ‘uint qHash(const T&, uint) [with T = WMathTest::Tag; uint = unsigned int]’:
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:952:32: required from ‘QHash<Key, T>::Node** QHash<Key, T>::findNode(const Key&, uint*) const [with Key = WMathTest::Tag; T = QHashDummyValue; QHash<Key, T>::Node = QHashNode<WMathTest::Tag, QHashDummyValue>; uint = unsigned int]’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:808:36: required from ‘QHash<Key, T>::iterator QHash<Key, T>::insert(const Key&, const T&) [with Key = WMathTest::Tag; T = QHashDummyValue]’
/opt/Qt/5.5/gcc_64/include/QtCore/qset.h:188:94: required from ‘QSet<T>::iterator QSet<T>::insert(const T&) [with T = WMathTest::Tag]’
/wmathtest/Exercise.cpp:22:22: required from here
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:103:5: error: no matching function for call to ‘qHash(const WMathTest::Tag&)’
Q_DECL_NOEXCEPT_EXPR(noexcept(qHash(t)))
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:103:5: note: candidates are:
In file included from /opt/Qt/5.5/gcc_64/include/QtCore/qset.h:37:0,
from /opt/Qt/5.5/gcc_64/include/QtCore/QSet:1,
from /wmathtest/Tag.h:5,
from /wmathtest/Exercise.h:5,
from /wmathtest/Exercise.cpp:1:
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:65:52: note: constexpr uint qHash(char, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(char key, uint seed = 0) Q_DECL_NOTHROW { return uint(key) ^ seed; }
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:65:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘char’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:66:52: note: constexpr uint qHash(uchar, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(uchar key, uint seed = 0) Q_DECL_NOTHROW { return uint(key) ^ seed; }
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:66:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘uchar {aka unsigned char}’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:67:52: note: constexpr uint qHash(signed char, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(signed char key, uint seed = 0) Q_DECL_NOTHROW { return uint(key) ^ seed; }
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:67:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘signed char’
In file included from /opt/Qt/5.5/gcc_64/include/QtCore/qset.h:37:0,
from /opt/Qt/5.5/gcc_64/include/QtCore/QSet:1,
from /home/daniele/projects/wmathtestgenerator/src/wmathtest/Tag.h:5,
from /Exercise.h:5,
from /wmathtest/Exercise.cpp:1:
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:68:52: note: constexpr uint qHash(ushort, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(ushort key, uint seed = 0) Q_DECL_NOTHROW { return uint(key) ^ seed; }
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:68:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘ushort {aka short unsigned int}’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:69:52: note: constexpr uint qHash(short int, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(short key, uint seed = 0) Q_DECL_NOTHROW { return uint(key) ^ seed; }
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:69:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘short int’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:70:52: note: constexpr uint qHash(uint, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(uint key, uint seed = 0) Q_DECL_NOTHROW { return key ^ seed; }
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:70:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘uint {aka unsigned int}’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:71:52: note: constexpr uint qHash(int, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(int key, uint seed = 0) Q_DECL_NOTHROW { return uint(key) ^ seed; }
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:71:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘int’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:72:52: note: constexpr uint qHash(ulong, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(ulong key, uint seed = 0) Q_DECL_NOTHROW
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:72:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘ulong {aka long unsigned int}’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:78:52: note: constexpr uint qHash(long int, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(long key, uint seed = 0) Q_DECL_NOTHROW { return qHash(ulong(key), seed); }
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:78:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘long int’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:79:52: note: constexpr uint qHash(quint64, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(quint64 key, uint seed = 0) Q_DECL_NOTHROW
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:79:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘quint64 {aka long long unsigned int}’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:83:52: note: constexpr uint qHash(qint64, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(qint64 key, uint seed = 0) Q_DECL_NOTHROW { return qHash(quint64(key), seed); }
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:83:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘qint64 {aka long long int}’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:84:42: note: uint qHash(float, uint)
Q_CORE_EXPORT Q_DECL_CONST_FUNCTION uint qHash(float key, uint seed = 0) Q_DECL_NOTHROW;
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:84:42: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘float’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:85:42: note: uint qHash(double, uint)
Q_CORE_EXPORT Q_DECL_CONST_FUNCTION uint qHash(double key, uint seed = 0) Q_DECL_NOTHROW;
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:85:42: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘double’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:87:42: note: uint qHash(long double, uint)
Q_CORE_EXPORT Q_DECL_CONST_FUNCTION uint qHash(long double key, uint seed = 0) Q_DECL_NOTHROW;
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:87:42: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘long double’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:89:52: note: constexpr uint qHash(QChar, uint)
Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qHash(const QChar key, uint seed = 0) Q_DECL_NOTHROW { return qHash(key.unicode(), seed); }
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:89:52: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘QChar’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:90:41: note: uint qHash(const QByteArray&, uint)
Q_CORE_EXPORT Q_DECL_PURE_FUNCTION uint qHash(const QByteArray &key, uint seed = 0) Q_DECL_NOTHROW;
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:90:41: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘const QByteArray&’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:91:41: note: uint qHash(const QString&, uint)
Q_CORE_EXPORT Q_DECL_PURE_FUNCTION uint qHash(const QString &key, uint seed = 0) Q_DECL_NOTHROW;
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:91:41: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘const QString&’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:92:41: note: uint qHash(const QStringRef&, uint)
Q_CORE_EXPORT Q_DECL_PURE_FUNCTION uint qHash(const QStringRef &key, uint seed = 0) Q_DECL_NOTHROW;
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:92:41: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘const QStringRef&’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:93:41: note: uint qHash(const QBitArray&, uint)
Q_CORE_EXPORT Q_DECL_PURE_FUNCTION uint qHash(const QBitArray &key, uint seed = 0) Q_DECL_NOTHROW;
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:93:41: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘const QBitArray&’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:94:41: note: uint qHash(QLatin1String, uint)
Q_CORE_EXPORT Q_DECL_PURE_FUNCTION uint qHash(QLatin1String key, uint seed = 0) Q_DECL_NOTHROW;
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:94:41: note: no known conversion for argument 1 from ‘const WMathTest::Tag’ to ‘QLatin1String’
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:98:32: note: template<class T> uint qHash(const T*, uint)
template <class T> inline uint qHash(const T *key, uint seed = 0) Q_DECL_NOTHROW
^
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:98:32: note: template argument deduction/substitution failed:
In file included from /opt/Qt/5.5/gcc_64/include/QtCore/qglobal.h:74:0,
from /opt/Qt/5.5/gcc_64/include/QtCore/qchar.h:37,
from /opt/Qt/5.5/gcc_64/include/QtCore/qstring.h:41,
from /opt/Qt/5.5/gcc_64/include/QtCore/QString:1,
from /home/daniele/projects/wmathtestgenerator/src/wmathtest/LaTeXText.h:4,
from /home/daniele/projects/wmathtestgenerator/src/wmathtest/Exercise.h:4,
from /thtest/Exercise.cpp:1:
/opt/Qt/5.5/gcc_64/include/QtCore/qhash.h:103:5: note: mismatched types ‘const T*’ and ‘WMathTest::Tag’
Q_DECL_NOEXCEPT_EXPR(noexcept(qHash(t)))
^
src/wmathtest/CMakeFiles/wmathtest.dir/build.make:146: recipe for target 'src/wmathtest/CMakeFiles/wmathtest.dir/Exercise.cpp.o' failed
make[2]: *** [src/wmathtest/CMakeFiles/wmathtest.dir/Exercise.cpp.o] Error 1
CMakeFiles/Makefile2:160: recipe for target 'src/wmathtest/CMakeFiles/wmathtest.dir/all' failed
make[1]: *** [src/wmathtest/CMakeFiles/wmathtest.dir/all] Error 2
Makefile:76: recipe for target 'all' failed
我已经创建了类，operator==和qHash的类。然后我为类创建了一个typedef，但这不起作用。
我做错了什么?
Tag.h
#ifndef WMATHTEST_TAG_H_
#define WMATHTEST_TAG_H_
#include <QString>
#include <QSet>
namespace WMathTest {
class Tag {
public:
Tag() = default;
Tag(const QString &text);
Tag(const Tag &tag) = default;
virtual ~Tag() = default;
void setText(const QString &text);
const QString& getText() const;
bool operator==(const Tag &other);
private:
QString m_text;
};
} // namespace WMathTest
inline uint qHash(const WMathTest::Tag &tag, uint seed) {
return qHash(tag.getText(), seed);
}
typedef QSet<WMathTest::Tag> TagList;
#endif // !WMATHTEST_TAG_H_
Tag.cpp
#include "wmathtest/Tag.h"
namespace WMathTest {
///////////////////////////////////////////////////////////////////////////////
// PUBLIC SECTION //
///////////////////////////////////////////////////////////////////////////////
Tag::Tag(const QString &text) :
m_text(text) {
}
void Tag::setText(const QString &text) {
m_text = text;
}
const QString& Tag::getText() const {
return m_text;
}
bool Tag::operator==(const Tag &other) {
return m_text == other.m_text;
}
} // namespace WMathTest
Exercise.h
#ifndef WMATHTEST_EXERCISE_H_
#define WMATHTEST_EXERCISE_H_
#include "wmathtest/LaTeXText.h"
#include "wmathtest/Tag.h"
#include <QString>
namespace WMathTest {
class Exercise {
public:
Exercise() = default;
virtual ~Exercise() = default;
void setID(const QString &id);
void setProblem(const LaTeXText &problem);
void setSolution(const LaTeXText &solution);
void addArgumentTag(const Tag &tag);
void addArgumentTag(const QString &tag);
QString getID() const;
LaTeXText getProblem() const;
LaTeXText getSolution() const;
const TagList& getArgumentTagList() const;
private:
QString m_id;
LaTeXText m_problem;
LaTeXText m_solution;
TagList m_tagList;
};
} // namespace WMathTest
#endif // !WMATHTEST_EXERCISE_H_
Exercise.cpp
#include "wmathtest/Exercise.h"
namespace WMathTest {
///////////////////////////////////////////////////////////////////////////////
// PUBLIC SECTION //
///////////////////////////////////////////////////////////////////////////////
void Exercise::setID(const QString &id) {
m_id = id;
}
void Exercise::setProblem(const LaTeXText &problem) {
m_problem = problem;
}
void Exercise::setSolution(const LaTeXText &solution) {
m_solution = solution;
}
void Exercise::addArgumentTag(const Tag &tag) {
m_tagList.insert(tag);
}
void Exercise::addArgumentTag(const QString &tag) {
m_tagList.insert(Tag(tag));
}
QString Exercise::getID() const {
return m_id;
}
LaTeXText Exercise::getProblem() const {
return m_problem;
}
LaTeXText Exercise::getSolution() const {
return m_solution;
}
const TagList& Exercise::getArgumentTagList() const {
return m_tagList;
}
} // namespace WMathTest
哈希是一元函数(只有一个参数)，它是数学意义上的函数(对于特定的参数返回相同的值，对于完整的参数集返回有效值)
哈希函数必须满足一个重要条件才能正常工作:如果两个对象被认为是相等的，那么这两个对象的哈希值也必须相等。因此，例如，如果您使用大小写不敏感的容器，其中字符串是键，则必须提供大小写不敏感的哈希函数。
请注意你在文档中看到的qHash函数的附加参数:seed总是有一个默认值!所以这个函数可以用一个参数调用!这个参数只是一个选项，当你为复杂类型构建自定义哈希函数时，它给了你一个调整哈希函数的机会。
像这样修复你的代码:
inline uint qHash(const WMathTest::Tag &tag) {
return qHash(tag.getText(), 0xa03f); // arbitrary value
}
或者像这样:
inline uint qHash(const WMathTest::Tag &tag, uint seed = 0) {
return qHash(tag.getText(), seed^0xa03f);
}
在更复杂类型的哈希函数可能看起来像这样(示例为什么种子可以有用):
inline uint qHash(const DoubleStringValue &tag, uint seed = 0) {
return qHash(tag.firstText(), seed^0xa03f)^qHash(tag.secondText(), seed^0x17a317a3);
}
请注意，如果有两个DoubleStringValue对象，其中firstText和secondText被翻转，则它们的哈希值将不同。
我建议阅读一些文档，了解带有哈希函数的容器是如何工作的，以及为什么它们比其他解决方案(例如红黑树)更快。
我自己找到了解决办法。显然这是我的错误，但与我的qHash实现无关。
我在operator==声明中做了一个错误:
bool operator==(const Tag &other);
声明缺少const限定符。应该是
bool operator==(const Tag &other) const;