C++ functor and list template

Question

I've implemented a list and iterator templates, the find method is supposed to receive a functor so I declared and implemented one but I keep getting the error that there's no such an object! " no matching function for call to object of type const findBond "

here's the implementation of the find method:

template <class T>
template <class Predicate>
Iterator<T> List<T> :: find(const Predicate &predicate) {
    for (Iterator<T> iterator=begin(); iterator != end(); ++iterator) {

        if (predicate(*iterator)) {

            return iterator;

        }

    }

    return end();

}

// predicate is a functor that is supposed to return a boolean value

here's the function object:

class findBond{

    Bond& bond;

public:

    findBond( Bond& bond1) : bond(bond1) {}

    bool operator() (Bond& bond1){

            return bond==bond1;

            }
};

I'm trying to use them here:

void InvestmentBroker :: addBond(const string& name, double value, int amount ){
    Bond bond = *new Bond(name, value, amount);

    if (bondsDatabase.find(findBond(bond)) != bondsDatabase.end()) {

        //throw an exception

    } else { 

       // insert bond to dataBase

    }
}

I included the needed files so it's not about the includes

What's wrong? What am I missing here?

Answer 1

Your find method takes a const Predicate& as its argument. That means you can only call const methods of the predicate. However, your functor's call operator is not declared const . You can fix your problem by declaring it const like this:

bool operator() (Bond& bond1) const {/* do stuff */ }

That const at the end of the declaration means that you can't modify this from within the function, which in turn means you can call the function on a const object.

Answer 2

It looks like a constness issue to me - findBond should be const on most arguments.

Change findBond to this

class findBond{
    const  Bond& bond;

public:

    findBond( const Bond& bond1) : bond(bond1) {}

    bool operator() const ( const Bond& bond1){
         return bond==bond1;
    }
};