Simple: Operator overloading with heap objects

Okay, it's seems like I'm missing something here:

Code:

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#include <QString>
#include <iostream>
 
class TestItem
{
public:
    TestItem(const QString &value)
    {
        m_value = value;
    }
 
    QString value() const
    {
        return m_value;
    }
 
    bool operator==(const TestItem &other) const
    {
        return this->value() == other.value();
    }
 
private:
    QString m_value;
};
 
int main(int argc, char *argv[])
{
    TestItem *one = new TestItem("abc");
    TestItem *two = new TestItem("abc");
 
    if(one == two)
        std::cout << "Match";
    else
        std::cout << "No Match";
 
    return 0;
}

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This returns ALWAYS "No Match". But if I create the objects on the stack and not on the heap it works:

Code:

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TestItem one("abc");
TestItem two("abc");

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What do I have to do to make it work with heap initialized objects :o ? Thank you.

You are comparing pointers instead of the objects itself, try:

Code:

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if (*one == *two)
    ...

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Yeah, I know, thanks :)
I just thought there might be a way to do it without the stars?

This should work:

Code:

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bool operator==(const TestItem *one, const TestItem *two) const {
    return one->value() == two->value();
}

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But this is risky, because you might have trouble checking for null values.

Quote:

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Originally Posted by wysota

This should work:

Code:

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bool operator==(const TestItem *one, const TestItem *two) const {
    return one->value() == two->value();
}

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But this is risky, because you might have trouble checking for null values.

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This one is probably safer, though a little slower...

Code:

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bool operator==(const TestItem *one, const TestItem *two) const {
    return (one && two) ? (one->value() == two->value()) : false;
}

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Sure nothing is stopping you from doing this.

But you probably wouldn't want to do this kind of overloading as you are giving a new meaning to the == operator on pointers. Many a times the users of your code would not think that you are comparing the values.

Quote:

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Originally Posted by sunil.thaha

But you probably wouldn't want to do this kind of overloading as you are giving a new meaning to the == operator on pointers. Many a times the users of your code would not think that you are comparing the values.

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That's why it's impossible in C++ ;)

Quote:

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That's why it's impossible in C++ ;)

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You are absolutely right. And thank you spotting out our mistake. I will never forget this :)

BTW: did you try out what was said here. Or you got it at the first go ?

Quote:

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Originally Posted by sunil.thaha

did you try out what was said here. Or you got it at the first go ?

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I knew that it's impossible, but I've checked it just to be sure.

Quote:

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Originally Posted by jacek

I knew that it's impossible, but I've checked it just to be sure.

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Just curious : what error was thrown by the compiler??? (don't tell me "check it on your own" because I just can't ATM...)

Quote:

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Originally Posted by fullmetalcoder

Just curious : what error was thrown by the compiler???

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Something like: "at least one of operator arguments must be a class or an enum".

I wonder if the behaviour is simmilar for all popular compilers.

Quote:

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Originally Posted by wysota

I wonder if the behaviour is simmilar for all popular compilers.

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It should be, at least if they are C++ compilers:

Quote:

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An operator function shall either be a non-static member function or be a non-member function and have at least one parameter whose type is a class, a reference to a class, an enumeration, or a reference to an enumeration.

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