[qt] qmap usage details

One . Catalog

1. Instantiation QMap object
2. insert data
3. Remove data
4. Traversal data
5. Find the corresponding key value by the key
6. Find key by key value
7. Modify key values
8. Find out if it contains a key
9. Get all keys and key values
10. A key corresponds to multiple values
11. Customize QMap class

1. Instantiation QMap object

    /*  establish QMap example ,  The first parameter is zero QString Type key , The second parameter is int Type value  */
    QMap<QString, int> map;

2. insert data

    /*  insert data   Two ways */
    map["math"] = 100;
    map.insert("English", 99);

Printout : QMap((“English”, 99)(“math”, 100))
3. Remove data

    /*  Remove data  */
    map.remove("math");

Printout ：QMap((“English”, 99))
4. Traversal data
 

    /*  Traversal data  ( Just insert a few )*/
    map.insert("Math", 100);
    map.insert("Chinese", 98);
    map.insert("physical", 97);
    map.insert("chemical", 96);
    map.insert("biological", 95);
    
    /*  Iterators are used to traverse the data ,QT Provides two ways of iterating  */
    /*  The first is Java Iterations of types  */
    QMapIterator<QString, int> iterator(map);
    while (iterator.hasNext()) {
        iterator.next();
        qDebug() << iterator.key() << ":" << iterator.value();
    }

    /*  The second is STL Iterations of types  */
    QMap<QString, int>::const_iterator iterator_1 = map.constBegin();
    while (iterator_1 != map.constEnd()) {
        qDebug() << iterator_1.key() << ":" << iterator_1.value();
        ++iterator_1;
    }

Printout ： Both methods output the same
“Chinese” : 98
“English” : 99
“Math” : 100
“biological” : 95
“chemical” : 96
“physical” : 97
5. Find the corresponding key value by the key

     map.value("Math");

Printout ：100
6. Find key by key value

map.key(100);

Printout ：“Math”
7. Modify key values

    /*  Usually a key corresponds to only one value , If called again insert() Method , The previous value will be overwritten  */
    map.insert("Math", 120);
    qDebug() << map.value("Math");

Printout ：120
8. Find out if it contains a key

    bool isok = map.contains("Math");
    qDebug() << isok;

Printout ：true
9. Get all keys and key values

    QList<QString> allKeys = map.keys();
    qDebug() << allKeys;
    QList<int> allValues = map.values();
    qDebug() << allValues;

Printout ：
(“Chinese”, “English”, “Math”, “biological”, “chemical”, “physical”)
(98, 99, 120, 95, 96, 97)

10. A key corresponds to multiple values

    /*  Use QMultiMap Class to instantiate a QMap object  */
    QMultiMap<QString, QString> multiMap;
    multiMap.insert("People", "Name");
    multiMap.insert("People", "Gender");
    multiMap.insert("People", "Age");
    multiMap.insert("People", "Height");
    multiMap.insert("People", "Weight");
    qDebug() << multiMap;
    /*  It can be seen from the printed results that multiMap Still one QMap object  */

Printout ：
5
“Weight”
(“Weight”, “Height”, “Age”, “Gender”, “Name”)
“Name”
From the above output, we can see , Use it directly value() Method is the last inserted item ; And by values() Method to get all the key values ; If you want to get a certain key value, you can use .at() Method .

11. Customize QMap class

QMap Only keys and key values , As a container , It can only produce one-to-one correspondence between the two data , But at present, I have three data that need to be related , At first I did this

    QMap<QString, int> mapOfId; 
    QMap<QString, QDateTime>mapOfTime;

Use two Qmap You can meet the requirements , Later, I found that there was still a little trouble , Simply use QList Customized a container that can store three values
Famous for its name CMAP

1. newly build ->Library–>C++ Library–> Custom library name
2. cmap.h Function declaration
3. cmap.cpp Function definition
4. Click on the run , Generate static link library

cmap.h File implementation

#ifndef CMAP_H
#define CMAP_H

#include "CMAP_global.h"
#include <QStringList>
#include <QDebug>
#include <QList>

class CMAP_EXPORT CMAP
{
public:
    CMAP();

    void insert(int key, QString value1, int value2); /*  Insert a row of data  */
    void insert(QList<int> keys, QStringList value1s, QList<int> value2s); /*  Insert multiple rows of data  */
    QList<int> keys() const; /*  Get all keys  */
    QStringList value1s() const; /*  Get all values 1 */
    QList<int> value2s() const; /*  Get all values 2 */
    QString value1(int key) const; /*  From key value to corresponding value 1 */
    int value2(int key) const; /*  From key value to corresponding value 2 */
    int key(QString value1) const; /*  By value 1 Get key value  */
    bool contains(int key) const; /*  Determine whether the key is included  */
    bool contains(QString value1) const; /*  Determine if the value... Is included 1 */
    bool remove(int key);  /*  Delete a row of data with the key  */
    bool remove(QString value1); /*  Pass value 1 Delete a row of data  */
    void clear(); /*  eliminate map */
    int size() const; /*  return map length  */
    void print() const; /*  Print all < key , value 1, value 2> */

private:

    QList<int> key_list;
    QStringList value1_list;
    QList<int> value2_list;


};

#endif // CMAP_H

cmap.cpp File implementation

#include "cmap.h"

CMAP::CMAP()
{
    clear();
}

void CMAP::insert(int key, QString value1, int value2)
{
    key_list << key;
    value1_list << value1;
    value2_list << value2;
}

void CMAP::insert(QList<int> keys, QStringList value1s, QList<int> value2s)
{
    Q_ASSERT(keys.size() == value1s.size());
    Q_ASSERT(keys.size() == value2s.size());
    key_list << keys;
    value1_list << value1s;
    value2_list << value2s;
}

QList<int> CMAP::keys() const
{
    return key_list;
}

QStringList CMAP::value1s() const
{
    return value1_list;
}

QList<int> CMAP::value2s() const
{
    return value2_list;
}


bool CMAP::contains(int key) const
{
    if(key_list.contains(key)) return true;
    else return false;
}

bool CMAP::contains(QString value1) const
{
    if(value1_list.contains(value1)) return true;
    else return false;
}

bool CMAP::remove(int key)
{
    if(!this->contains(key)) return false;

    int i = key_list.indexOf(key);
    key_list.removeAt(i);
    value1_list.removeAt(i);
    value2_list.removeAt(i);
    return true;
}

bool CMAP::remove(QString value1)
{
    if(!this->contains(value1)) return false;

    int i = value1_list.indexOf(value1);
    key_list.removeAt(i);
    value1_list.removeAt(i);
    value2_list.removeAt(i);
    return true;
}

void CMAP::clear()
{
    key_list.clear();
    value1_list.clear();
    value2_list.clear();
}

int CMAP::size() const
{
    return key_list.size();
}

void CMAP::print() const
{
    for(int i = 0; i < size(); i++) {
        qDebug() << QString("key:%1 value1:%2 value2:%3").
                    arg(key_list.at(i)).
                    arg(value1_list.at(i)).
                    arg(value2_list.at(i));
    }
}


QString CMAP::value1(int key) const
{
    if(!this->contains(key)) return "";

    int i = key_list.indexOf(key);
    return value1_list.at(i);
}

int CMAP::value2(int key) const
{
    if(!this->contains(key)) return -1;

    int i = key_list.indexOf(key);
    return value2_list.at(i);
}

int CMAP::key(QString value1) const
{
    if(!this->contains(value1)) return -1;
    int i = value1_list.indexOf(value1);
    return key_list.at(i);
}

CMAP_global.h Just keep the file unchanged
The generated file can be used directly