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1. 介绍
Qt提供的一个单值的数学集合的快速查找容器,使用方式与QList相同,但其内元素不会有重复。详细说明见 官方文档
注意,此容器实现方式是基于哈希表,而不是红黑树,若使用自定义类必须提供对应的hash函数:
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. 简单范例
- QSet <QString> m_set;
- m_set.insert("1");
- m_set.insert("3");
- m_set.insert("2");//注意插入顺序
- auto b_set = m_set.begin();
- qDebug()<<m_set.size();
- qDebug()<<*b_set++;
- qDebug()<<*b_set++;
- qDebug()<<*b_set++;//注意存储顺序
- m_set.insert("1");//插入重复的
- b_set = m_set.begin();
- qDebug()<<m_set.size();
- qDebug()<<*b_set++;
- qDebug()<<*b_set++;
- qDebug()<<*b_set++;
结果
- 3
- "1"
- "2"
- "3"
- 3
- "1"
- "2"
- "3"
3. 自定义类型
- #include <QCoreApplication>
- #include <QSet>
- #include <QDebug>
- class testCustomTypeByQSet {
- public:
- testCustomTypeByQSet(int v):m_value(v){};
- int value() const{
- return m_value;
- }
- bool operator == (const testCustomTypeByQSet &t) const {
- return (m_value==t.value());
- }
- private:
- int m_value;
- };
- uint qHash(const testCustomTypeByQSet &key, uint seed = 0) {
- return key.value();
- }
- int main(int argc, char *argv[]) {
- QCoreApplication a(argc, argv);
- QSet<testCustomTypeByQSet> m_set;
- m_set.insert(testCustomTypeByQSet(1));
- m_set.insert(testCustomTypeByQSet(3));
- m_set.insert(testCustomTypeByQSet(2));
- m_set.insert(testCustomTypeByQSet(7));
- m_set.insert(testCustomTypeByQSet(-1));
- auto b_set = m_set.begin();
- qDebug()<<m_set.size();
- qDebug()<<(*b_set++).value();
- qDebug()<<(*b_set++).value();
- qDebug()<<(*b_set++).value();
- qDebug()<<(*b_set++).value();
- qDebug()<<(*b_set++).value();
- return 0;
- }
结果
- 5
- -1
- 1
- 2
- 3
- 7
qt自身的类已经实现了对应的qHash,存储在QHash类中,详见官方文档:
- uint qHash(const QXmlNodeModelIndex &index)
- uint qHash(const QUrl &url, uint seed = 0)
- uint qHash(const QDateTime &key, uint seed = 0)
- uint qHash(const QDate &key, uint seed = 0)
- uint qHash(const QTime &key, uint seed = 0)
- uint qHash(const QPair<T1, T2> &key, uint seed = 0)
- uint qHash(const std::pair<T1, T2> &key, uint seed = 0)
- uint qHash(char key, uint seed = 0)
- uint qHash(uchar key, uint seed = 0)
- uint qHash(signed char key, uint seed = 0)
- uint qHash(ushort key, uint seed = 0)
- uint qHash(short key, uint seed = 0)
- uint qHash(uint key, uint seed = 0)
- uint qHash(int key, uint seed = 0)
- uint qHash(ulong key, uint seed = 0)
- uint qHash(long key, uint seed = 0)
- uint qHash(quint64 key, uint seed = 0)
- uint qHash(qint64 key, uint seed = 0)
- uint qHash(float key, uint seed = 0)
- uint qHash(double key, uint seed = 0)
- uint qHash(const QChar key, uint seed = 0)
- uint qHash(const QByteArray &key, uint seed = 0)
- uint qHash(const QBitArray &key, uint seed = 0)
- uint qHash(const QString &key, uint seed = 0)
- uint qHash(const QStringRef &key, uint seed = 0)
- uint qHash(QLatin1String key, uint seed = 0)
- uint qHash(const T *key, uint seed = 0)
- uint qHash(const QHash<Key, T> &key, uint seed = 0)
- uint qHash(const QSet<T> &key, uint seed = 0)
- uint qHash(const QVersionNumber &key, uint seed = 0)
- uint qHash(const QSslCertificate &key, uint seed = 0)
- uint qHash(QSslEllipticCurve curve, uint seed = 0)
- uint qHash(const QSslError &key, uint seed = 0)
- uint qHash(const QGeoCoordinate &coordinate, uint seed = 0)
同时也在对应类中做了“==”的重载操作符,比如QString类。
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