problem with QHash

cosmoff

Hello everybody,

I have a problem when I compile this code :

QHash<QString, double> hash ( it.parameters() );

for(const auto &h : hash)
{
	if(h.key() == "value1")
	{
		qDebug() << h.value() ;
	}

}

the compilator return : erreur : request for member ‘key’ in ‘h’, which is of non-class type ‘const double’
and erreur : request for member ‘value’ in ‘h’, which is of non-class type ‘const double’
However the key() return the first element so a QString. So what is the problem and how to fix it

thanks for your help

sierdzio

@cosmoff said in problem with QHash:

qDebug() << h.value() ;

"h" is your value, a double. It is not the hash.

So write this instead:

qDebug() << hash.value(h) ;

This will print the value for given key (h).

Also, make hash const or use qAsConst() otherwise it will detach in ranged for loop == worse performance.

cosmoff

@sierdzio thanks for your answer, and how I can read the key ?

cosmoff

In fact, I want to read all the elements key and value of my loop, like :

for(const auto &h : hash)
    {
        qDebug() << h.hey() << h.value();
    }

Christian Ehrlicher

Then you need to use iterators - Qt's containers return the value in a range-based for loop:

for (auto it = hash.cbegin();  it != hash.cend(); ++it)
  qDebug() << it.key() << it.value();

J.Hilk

@cosmoff
directly taken from the docs:

QHashIterator<QString, int> i(hash);
while (i.hasNext()) {
    i.next();
    cout << i.key() << ": " << i.value() << endl;
}

//std style
QHash<QString, int>::const_iterator i = hash.constBegin();
while (i != hash.constEnd()) {
    cout << i.key() << ": " << i.value() << endl;
    ++i;
}

cosmoff

it works!
thank a lot

Christian Ehrlicher

@cosmoff Then please mark this topic as solved, thx.

Solved problem with QHash