src_corelib_tools_qmap.cpp

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QMap<QString, int> map;
 
 
map["one"] = 1;
map["three"] = 3;
map["seven"] = 7;
 
 
map.insert("twelve", 12);
 
 
int num1 = map["thirteen"];
int num2 = map.value("thirteen");
 
 
int timeout = 30;
if (map.contains("TIMEOUT"))
    timeout = map.value("TIMEOUT");
 
 
int timeout = map.value("TIMEOUT", 30);
 
 
// WRONG
QMap<int, QWidget *> map;
...
for (int i = 0; i < 1000; ++i) {
    if (map[i] == okButton)
        cout << "Found button at index " << i << Qt::endl;
}
 
 
QMapIterator<QString, int> i(map);
while (i.hasNext()) {
    i.next();
    cout << i.key() << ": " << i.value() << Qt::endl;
}
 
 
QMap<QString, int>::const_iterator i = map.constBegin();
while (i != map.constEnd()) {
    cout << i.key() << ": " << i.value() << Qt::endl;
    ++i;
}
 
 
map.insert("plenty", 100);
map.insert("plenty", 2000);
// map.value("plenty") == 2000
 
 
QMap<QString, int> map;
...
foreach (int value, map)
    cout << value << Qt::endl;
 
 
#ifndef EMPLOYEE_H
#define EMPLOYEE_H
 
class Employee
{
public:
    Employee() {}
    Employee(const QString &name, QDate dateOfBirth);
    ...
 
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
 
 
QMap<QString, int> map;
...
QMap<QString, int>::const_iterator i = map.find("HDR");
while (i != map.end() && i.key() == "HDR") {
    cout << i.value() << Qt::endl;
    ++i;
}
 
 
QMap<int, QString> map;
map.insert(1, "one");
map.insert(5, "five");
map.insert(10, "ten");
 
map.lowerBound(0);      // returns iterator to (1, "one")
map.lowerBound(1);      // returns iterator to (1, "one")
map.lowerBound(2);      // returns iterator to (5, "five")
map.lowerBound(10);     // returns iterator to (10, "ten")
map.lowerBound(999);    // returns end()
 
 
QMap<QString, int> map;
...
QMap<QString, int>::const_iterator i = map.lowerBound("HDR");
QMap<QString, int>::const_iterator upperBound = map.upperBound("HDR");
while (i != upperBound) {
    cout << i.value() << Qt::endl;
    ++i;
}
 
 
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()
 
 
QMap<QString, int> map;
map.insert("January", 1);
map.insert("February", 2);
...
map.insert("December", 12);
 
QMap<QString, int>::iterator i;
for (i = map.begin(); i != map.end(); ++i)
    cout << i.key() << ": " << i.value() << Qt::endl;
 
 
QMap<QString, int>::iterator i;
for (i = map.begin(); i != map.end(); ++i)
    i.value() += 2;
 
 
QMap<QString, int>::iterator i = map.begin();
while (i != map.end()) {
    if (i.key().startsWith('_'))
        i = map.erase(i);
    else
        ++i;
}
 
 
QMap<QString, int>::iterator i = map.begin();
while (i != map.end()) {
    QMap<QString, int>::iterator prev = i;
    ++i;
    if (prev.key().startsWith('_'))
        map.erase(prev);
}
 
 
// WRONG
while (i != map.end()) {
    if (i.key().startsWith('_'))
        map.erase(i);
    ++i;
}
 
 
if (i.key() == "Hello")
    i.value() = "Bonjour";
 
 
QMap<QString, int> map;
map.insert("January", 1);
map.insert("February", 2);
...
map.insert("December", 12);
 
QMap<QString, int>::const_iterator i;
for (i = map.constBegin(); i != map.constEnd(); ++i)
    cout << i.key() << ": " << i.value() << Qt::endl;
 
 
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
 
 
QList<int> values = map.values("plenty");
for (int i = 0; i < values.size(); ++i)
    cout << values.at(i) << Qt::endl;
 
 
QMultiMap<QString, int>::iterator i = map.find("plenty");
while (i != map.end() && i.key() == "plenty") {
    cout << i.value() << Qt::endl;
    ++i;
}
 
for (QMap<int, QString>::const_iterator it = map.cbegin(), end = map.cend(); it != end; ++it) {
    cout << "The key: " << it.key() << Qt::endl
    cout << "The value: " << it.value() << Qt::endl;
    cout << "Also the value: " << (*it) << Qt::endl;
}
 
// 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 numPrimes = std::count_if(map.keyBegin(), map.keyEnd(), isPrimeNumber);
qDeleteAll(map2.keyBegin(), map2.keyEnd());