• 1. 介紹
• 2. 簡單範例
• 3. 自定義類型

1. 介紹

Qt提供的一個單值的數學集合的快速查找容器，使用方式與QList相同，但其內元素不會有重復。詳細說明見 官方文檔

註意，此容器實現方式是基於哈希表，而不是紅黑樹，若使用自定義類必須提供對應的hash函數：

QSet‘s value data type must be an assignable data type. You cannot, for example, store a QWidget as a value; instead, store a QWidget *. In addition, the type must provide operator==()

, and there must also be a global qHash() function that returns a hash value for an argument of the key’s type. See the QHash documentation for a list of types supported by qHash().

2. 簡單範例

1. QSet <QString> m_set;
2. m_set.insert("1");
3. m_set.insert("3");
4. m_set.insert("2");//註意插入順序
5. auto b_set = m_set.begin();
6. qDebug()<<m_set.size();
7. qDebug()<<*b_set++;
8. qDebug()<<*b_set++;
9. qDebug()<<*b_set++;//註意存儲順序
10. m_set.insert("1");//插入重復的
11. b_set = m_set.begin();
12. qDebug()<<m_set.size();
13. qDebug()<<*b_set++;
14. qDebug()<<*b_set++;
15. qDebug()<<*b_set++;

結果

1. 3
2. "1"
3. "2"
4. "3"
5. 3
6. "1"
7. "2"
8. "3"

3. 自定義類型

1. #include <QCoreApplication>
2. #include <QSet>
3. #include <QDebug>
4. class testCustomTypeByQSet {
5. public:
6. testCustomTypeByQSet(int v):m_value(v){};
7. int value() const{
8. return m_value;
9. }
10. bool operator == (const testCustomTypeByQSet &t) const {
11. return (m_value==t.value());
12. }
13. private:
14. int m_value;
15. };
16. uint qHash(const testCustomTypeByQSet &key, uint seed = 0) {
17. return key.value();
18. }
19. int main(int argc, char *argv[]) {
20. QCoreApplication a(argc, argv);
21. QSet<testCustomTypeByQSet> m_set;
22. m_set.insert(testCustomTypeByQSet(1));
23. m_set.insert(testCustomTypeByQSet(3));
24. m_set.insert(testCustomTypeByQSet(2));
25. m_set.insert(testCustomTypeByQSet(7));
26. m_set.insert(testCustomTypeByQSet(-1));
27. auto b_set = m_set.begin();
28. qDebug()<<m_set.size();
29. qDebug()<<(*b_set++).value();
30. qDebug()<<(*b_set++).value();
31. qDebug()<<(*b_set++).value();
32. qDebug()<<(*b_set++).value();
33. qDebug()<<(*b_set++).value();
34. return 0;
35. }

結果

1. 5
2. -1
3. 1
4. 2
5. 3
6. 7

qt自身的類已經實現了對應的qHash，存儲在QHash類中，詳見官方文檔：

1. uint qHash(const QXmlNodeModelIndex &index)
2. uint qHash(const QUrl &url, uint seed = 0)
3. uint qHash(const QDateTime &key, uint seed = 0)
4. uint qHash(const QDate &key, uint seed = 0)
5. uint qHash(const QTime &key, uint seed = 0)
6. uint qHash(const QPair<T1, T2> &key, uint seed = 0)
7. uint qHash(const std::pair<T1, T2> &key, uint seed = 0)
8. uint qHash(char key, uint seed = 0)
9. uint qHash(uchar key, uint seed = 0)
10. uint qHash(signed char key, uint seed = 0)
11. uint qHash(ushort key, uint seed = 0)
12. uint qHash(short key, uint seed = 0)
13. uint qHash(uint key, uint seed = 0)
14. uint qHash(int key, uint seed = 0)
15. uint qHash(ulong key, uint seed = 0)
16. uint qHash(long key, uint seed = 0)
17. uint qHash(quint64 key, uint seed = 0)
18. uint qHash(qint64 key, uint seed = 0)
19. uint qHash(float key, uint seed = 0)
20. uint qHash(double key, uint seed = 0)
21. uint qHash(const QChar key, uint seed = 0)
22. uint qHash(const QByteArray &key, uint seed = 0)
23. uint qHash(const QBitArray &key, uint seed = 0)
24. uint qHash(const QString &key, uint seed = 0)
25. uint qHash(const QStringRef &key, uint seed = 0)
26. uint qHash(QLatin1String key, uint seed = 0)
27. uint qHash(const T *key, uint seed = 0)
28. uint qHash(const QHash<Key, T> &key, uint seed = 0)
29. uint qHash(const QSet<T> &key, uint seed = 0)
30. uint qHash(const QVersionNumber &key, uint seed = 0)
31. uint qHash(const QSslCertificate &key, uint seed = 0)
32. uint qHash(QSslEllipticCurve curve, uint seed = 0)
33. uint qHash(const QSslError &key, uint seed = 0)
34. uint qHash(const QGeoCoordinate &coordinate, uint seed = 0)

同時也在對應類中做了“==”的重載操作符，比如QString類。

QSet使用及Qt自定義類型使用QHash等算法