src_corelib_tools_qmap.cpp

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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 
#include <QMap>
#include <QMapIterator>
#include <iostream>
#include <QDate>
 
using namespace std;
 
void examples()
{
    //! [0]
    QMap<QString, int> map;
    //! [0]
 
    {
        //! [1]
        map["one"] = 1;
        map["three"] = 3;
        map["seven"] = 7;
        //! [1]
    }
 
    {
        //! [2]
        map.insert("twelve", 12);
        //! [2]
    }
 
    {
        //! [3]
        int num1 = map["thirteen"];
        int num2 = map.value("thirteen");
        //! [3]
    }
 
    {
        //! [4]
        int timeout = 30;
        if (map.contains("TIMEOUT"))
            timeout = map.value("TIMEOUT");
        //! [4]
    }
 
    {
        //! [5]
        int timeout = map.value("TIMEOUT", 30);
        //! [5]
    }
 
    {
        //! [7]
        QMapIterator<QString, int> i(map);
        while (i.hasNext()) {
            i.next();
            cout << qPrintable(i.key()) << ": " << i.value() << endl;
        }
        //! [7]
    }
 
    {
        //! [8]
        for (auto i = map.cbegin(), end = map.cend(); i != end; ++i)
            cout << qPrintable(i.key()) << ": " << i.value() << endl;
        //! [8]
    }
 
    {
        //! [9]
        map.insert("plenty", 100);
        map.insert("plenty", 2000);
        // map.value("plenty") == 2000
        //! [9]
    }
 
    {
        //! [12]
        QMap<QString, int> map;
        //...
        for (int value : std::as_const(map))
            cout << value << endl;
        //! [12]
    }
}
 
#if __has_include(<QWidget>)
#include <QWidget>
 
void widget_example(QWidget *okButton)
{
    //! [6]
    // WRONG
    QMap<int, QWidget *> map;
    //...
    for (int i = 0; i < 1000; ++i) {
        if (map[i] == okButton)
            cout << "Found button at index " << i << endl;
    }
    //! [6]
}
#endif
 
 
    //! [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()
{
    {
        //! [17]
        QMap<int, QString> map;
        map.insert(1, "one");
        map.insert(5, "five");
        map.insert(10, "ten");
 
        map.upperBound(0);      // returns iterator to (1, "one")
        map.upperBound(1);      // returns iterator to (5, "five")
        map.upperBound(2);      // returns iterator to (5, "five")
        map.upperBound(10);     // returns end()
        map.upperBound(999);    // returns end()
        //! [17]
    }
 
    {
        //! [18]
        QMap<QString, int> map;
        map.insert("January", 1);
        map.insert("February", 2);
        //...
        map.insert("December", 12);
 
        for (auto i = map.cbegin(), end = map.cend(); i != end; ++i)
            cout << qPrintable(i.key()) << ": " << i.value() << endl;
        //! [18]
    }
 
    {
        QMap<QString, int> map;
 
        //! [19]
        for (auto i = map.begin(), end = map.end(); i != end; ++i)
            i.value() += 2;
        //! [19]
    }
 
    {
        QMap<QString, int> map;
 
        //! [20]
        QMap<QString, int>::const_iterator i = map.cbegin();
        while (i != map.cend()) {
            if (i.value() > 10)
                i = map.erase(i);
            else
                ++i;
        }
        //! [20]
    }
 
    {
        QMap<QString, int> map;
 
        //! [21]
        erase_if(map, [](const QMap<QString, int>::iterator it) { return it.value() > 10; });
        //! [21]
    }
 
    {
        QMap<QString, QString> map;
        auto i = map.begin();
 
        //! [23]
        if (i.key() == "Hello")
            i.value() = "Bonjour";
        //! [23]
    }
 
    {
        //! [24]
        QMap<QString, int> map;
        map.insert("January", 1);
        map.insert("February", 2);
        //...
        map.insert("December", 12);
 
        for (auto i = map.cbegin(), end = map.cend(); i != end; ++i)
            cout << qPrintable(i.key()) << ": " << i.value() << endl;
        //! [24]
    }
 
    {
        QMap<int, QString> map;
 
        //! [keyiterator1]
        for (QMap<int, QString>::const_iterator it = map.cbegin(), end = map.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]
    }
 
    {
        QMap<int, int> map;
        QMap<QObject *, int> map2;
        auto isPrimeNumber = [](int num) { return true; };
 
        //! [keyiterator2]
        // Inefficient, keys() is expensive
        QList<int> keys = map.keys();
        int numPrimes = std::count_if(map.cbegin(), map.cend(), isPrimeNumber);
        qDeleteAll(map2.keys());
 
        // Efficient, no memory allocation needed
        int primeNums = std::count_if(map.keyBegin(), map.keyEnd(), isPrimeNumber);
        qDeleteAll(map2.keyBegin(), map2.keyEnd());
        //! [keyiterator2]
    }
 
    {
        //! [28]
        QMap<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
        }
        //! [28]
    }
}