src_corelib_tools_qmultimap.cpp

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// Copyright (C) 2020 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 
#include <QMultiMap>
#include <QMultiMapIterator>
#include <iostream>
#include <QDate>
 
using namespace std;
 
void examples()
{
    //! [0]
    QMultiMap<QString, int> multimap;
    //! [0]
 
    {
        //! [2]
        multimap.insert("a", 1);
        multimap.insert("b", 3);
        multimap.insert("c", 7);
        multimap.insert("c", -5);
        //! [2]
    }
 
    {
        //! [3]
        int num2 = multimap.value("a"); // 1
        int num3 = multimap.value("thirteen"); // not found; 0
        auto it = multimap.constFind("b");
        if (it != multimap.cend()) {
            num3 = it.value();
        }
        //! [3]
    }
 
    {
        //! [4]
        int timeout = 30;
        if (multimap.contains("TIMEOUT"))
            timeout = multimap.value("TIMEOUT");
 
        // better:
        auto it = multimap.find("TIMEOUT");
        if (it != multimap.end())
            timeout = it.value();
        //! [4]
    }
 
    {
        //! [5]
        int timeout = multimap.value("TIMEOUT", 30);
        //! [5]
    }
 
    {
        //! [7]
        QMultiMapIterator<QString, int> i(multimap);
        while (i.hasNext()) {
            i.next();
            cout << qPrintable(i.key()) << ": " << i.value() << endl;
        }
        //! [7]
    }
 
    {
        //! [8]
        for (auto i = multimap.cbegin(), end = multimap.cend(); i != end; ++i)
            cout << qPrintable(i.key()) << ": " << i.value() << endl;
        //! [8]
    }
 
    {
        //! [9]
        multimap.insert("plenty", 100);
        multimap.insert("plenty", 2000);
        // multimap.size() == 2
        //! [9]
    }
 
    {
        //! [10]
        QList<int> values = multimap.values("plenty");
        for (auto i : std::as_const(values))
            cout << i << endl;
        //! [10]
    }
 
    {
        //! [11]
        auto i = multimap.find("plenty");
        while (i != multimap.end() && i.key() == "plenty") {
            cout << i.value() << endl;
            ++i;
        }
 
        //! [11]
    }
 
    {
        //! [11_better]
        // better:
        auto [i, end] = multimap.equal_range("plenty");
        while (i != end) {
            cout << i.value() << endl;
            ++i;
        }
        //! [11_better]
    }
 
    {
        //! [12]
        QMap<QString, int> multimap;
        //...
        for (int value : std::as_const(multimap))
            cout << value << endl;
        //! [12]
    }
}
 
//! [13]
#ifndef EMPLOYEE_H
#define EMPLOYEE_H
 
class Employee
{
public:
    Employee() {}
    Employee(const QString &name, QDate dateOfBirth);
    QString name() const { return myName; }
    QDate dateOfBirth() const { return myDateOfBirth; }
    //...
 
private:
    QString myName;
    QDate myDateOfBirth;
};
 
inline bool operator<(const Employee &e1, const Employee &e2)
{
    if (e1.name() != e2.name())
        return e1.name() < e2.name();
    return e1.dateOfBirth() < e2.dateOfBirth();
}
 
#endif // EMPLOYEE_H
//! [13]
 
 
void erase()
{
    {
        //! [15]
        QMultiMap<int, QString> multimap;
        multimap.insert(1, "one");
        multimap.insert(5, "five");
        multimap.insert(5, "five (2)");
        multimap.insert(10, "ten");
 
        multimap.lowerBound(0);      // returns iterator to (1, "one")
        multimap.lowerBound(1);      // returns iterator to (1, "one")
        multimap.lowerBound(2);      // returns iterator to (5, "five")
        multimap.lowerBound(5);      // returns iterator to (5, "five")
        multimap.lowerBound(6);      // returns iterator to (10, "ten")
        multimap.lowerBound(10);     // returns iterator to (10, "ten")
        multimap.lowerBound(999);    // returns end()
        //! [15]
    }
 
    {
        //! [16]
        QMap<QString, int> multimap;
        //...
        QMap<QString, int>::const_iterator i = multimap.lowerBound("HDR");
        QMap<QString, int>::const_iterator upperBound = multimap.upperBound("HDR");
        while (i != upperBound) {
            cout << i.value() << endl;
            ++i;
        }
        //! [16]
    }
 
    {
        //! [17]
        QMultiMap<int, QString> multimap;
        multimap.insert(1, "one");
        multimap.insert(5, "five");
        multimap.insert(5, "five (2)");
        multimap.insert(10, "ten");
 
        multimap.upperBound(0);      // returns iterator to (1, "one")
        multimap.upperBound(1);      // returns iterator to (5, "five")
        multimap.upperBound(2);      // returns iterator to (5, "five")
        multimap.lowerBound(5);      // returns iterator to (5, "five (2)")
        multimap.lowerBound(6);      // returns iterator to (10, "ten")
        multimap.upperBound(10);     // returns end()
        multimap.upperBound(999);    // returns end()
        //! [17]
    }
 
    {
        QMultiMap<QString, int> multimap;
 
        //! [19]
        for (auto i = multimap.begin(), end = multimap.end(); i != end; ++i)
            i.value() += 2;
        //! [19]
    }
 
    {
        QMultiMap<QString, int> multimap;
 
        //! [20]
        QMultiMap<QString, int>::const_iterator i = multimap.cbegin();
        while (i != multimap.cend()) {
            if (i.value() > 10)
                i = multimap.erase(i);
            else
                ++i;
        }
        //! [20]
    }
 
    {
        QMultiMap<QString, int> multimap;
 
        //! [21]
        erase_if(multimap, [](const QMultiMap<QString, int>::iterator it) { return it.value() > 10; });
        //! [21]
    }
 
    {
        auto i = QMultiMap<QString, QString>::iterator();
 
        //! [23]
        if (i.key() == "Hello")
            i.value() = "Bonjour";
        //! [23]
    }
 
    {
        //! [24]
        QMultiMap<QString, int> multimap;
        multimap.insert("January", 1);
        multimap.insert("February", 2);
        //...
        multimap.insert("December", 12);
 
        for (auto i = multimap.cbegin(), end = multimap.cend(); i != end; ++i)
            cout << qPrintable(i.key()) << ": " << i.value() << endl;
        //! [24]
    }
 
    {
        //! [25]
        QMultiMap<QString, int> map1, map2, map3;
 
        map1.insert("plenty", 100);
        map1.insert("plenty", 2000);
        // map1.size() == 2
 
        map2.insert("plenty", 5000);
        // map2.size() == 1
 
        map3 = map1 + map2;
        // map3.size() == 3
        //! [25]
    }
 
    {
        QMultiMap<int, QString> multimap;
 
        //! [keyiterator1]
        for (auto it = multimap.cbegin(), end = multimap.cend(); it != end; ++it) {
            cout << "The key: " << it.key() << endl;
            cout << "The value: " << qPrintable(it.value()) << endl;
            cout << "Also the value: " << qPrintable(*it) << endl;
        }
        //! [keyiterator1]
    }
 
    {
        QMultiMap<int, int> multimap;
        QMultiMap<QObject *, int> multimap2;
        auto isPrimeNumber = [](int num) { return true; };
 
        //! [keyiterator2]
        // Inefficient, keys() is expensive
        QList<int> keys = multimap.keys();
        int numPrimes = std::count_if(multimap.cbegin(), multimap.cend(), isPrimeNumber);
        qDeleteAll(multimap2.keys());
 
        // Efficient, no memory allocation needed
        int primeNums = std::count_if(multimap.keyBegin(), multimap.keyEnd(), isPrimeNumber);
        qDeleteAll(multimap2.keyBegin(), multimap2.keyEnd());
        //! [keyiterator2]
    }
 
    {
        //! [26]
        QMultiMap<QString, int> map;
        map.insert("January", 1);
        map.insert("February", 2);
        // ...
        map.insert("December", 12);
 
        for (auto [key, value] : map.asKeyValueRange()) {
            cout << qPrintable(key) << ": " << value << endl;
            --value; // convert to JS month indexing
        }
        //! [26]
    }
}