CODEWITHSUNDEEP
c++qt
anbu selvan
anbu selvan

Reputation: 745

Using QHash in a custom class

I am newbie in Qt and learning to handle how QHash works. On working with this example I dont understand why this throws me an error. I may miss something, but please guide me to learn this.

main.cpp

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QHash<QString,Person> hash;
QString key="1";

Person p;
p.name = name;
p.number = an;

hash.insert(key,p); 

    return a.exec();
}

person.h

class Person
{
public:
    Person();
    Person(QString name,QString num);
    bool operator==(const Person & other) const; //== overloading to assign in QHash
    QString name,number;
};

person.cpp

Person::Person()
{
}
Person::Person(QString name, QString num)
{
    this->name=name;
    this->number=num;
}
bool Person::operator==(const Person & other) const
{
    bool state;
    if (name == other.name )
        state = true;
    else
        state = false;

    return state;
}

and the error is:-'qHash':none of the 17 overloads could convert all the argument type.I knw im missing something.Please guide me.

Upvotes: 5

Views: 16232

Answers (2)

thuga
thuga

Reputation: 12931

You need the global qHash() function.

A QHash's key type has additional requirements other than being an assignable data type: it must provide operator==(), and there must also be a qHash() function in the type's namespace that returns a hash value for an argument of the key's type.

See this for more info about that.

Upvotes: 5

Valentin H
Valentin H

Reputation: 7458

The code you've provided is not complete and not compilable - e.g. The symbol name is not found, no includes.

The op == is not required when you use the class as value. The only one requirement for value-classes - a default constructor.

I think you problem was something else. If you provided the complete code and the complete list of errors I could tell you what exactly.

Below you'll find the working version of you code-snippet. (For simplicity, everything in one file)

main.cpp

#include <QApplication>
#include <QHash>
#include <QString>

class Person
{
public:
    Person(QString name=QString::null,QString num=QString::null);
    QString name,number;
};


Person::Person(QString _name, QString _num)
:name(_name),number(_num)
{   
}

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QHash<QString,Person> hash;
    QString key="1";

    Person p("Orhan Kemal", "1914");

    hash.insert(key,p); 
        return a.exec();
}

Regards, Valentin

EDIT: Initialized members not in body

Upvotes: 0

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