CODEWITHSUNDEEP
c++oopvectorstl
ben18785
ben18785

Reputation: 356

Remove an object in a std::vector by value

I would like to remove an object from a stl vector if it is present.

class test
{
    vector<Objects> myvector;

public:
        test();
        removeTest(Objects);
}

test::removeTest(Objects aObject)
{
    myvector.erase(remove(myvector.begin(), myvector.end(), aTest),myvector.end());
}

However, whenever I try to compile this, I get the following error:

no match for 'operator=='

This only occurs if I use an iterator through a vector of objects of type 'Objects'. I can get it to work for the case of looking for an integer then removing this.

Anyone know why I am getting these errors? And am I using the correct method to remove an object from a stl vector of objects by value?

Upvotes: 0

Views: 923

Answers (1)

Barry
Barry

Reputation: 302767

no match for 'operator=='

Error says it all. You need to provide an equality comparison for your Object class, std::remove can't otherwise know how to compare your objects to determine which ones need to be removed.

For example:

struct Object {
    int i;
    std::string s;

    bool operator==(const Object& rhs) const {
        return i == rhs.i && s == rhs.s;
    }
};

It worked for integers because equality comparison between integers is built-in. Not so for user-defined types.

With that, this:

    void test::removeTest(const Object& aObject)
//  ^^^^                  ^^^^^^^^^^^^^  
    {
        myvector.erase(
            remove(myvector.begin(), myvector.end(), aObject),
//                                                   ^^^^^^^
            myvector.end()
            );
    }

Should do exactly what you want. Note that you were missing a return type for removeTest (I'm assuming you want void) and you should take the object you want to remove by reference-to-const to avoid the unnecessary copy.

Upvotes: 1

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