C++ returning collection by value

I want to make my collection immutable outside of my class.

from this:

public:    
    vector<int>& getValues(){
        retur开发者_JAVA技巧n values;
    }
private: 
    vector <int>& values;

to this:

public:    
    vector<int> getValues(){
        return values;
    }
private: 
    vector <int>& values;

Will it work fine?

It will work, but you would be better off returning a const reference:

const vector<int> & getValues() const {
    return values;
}

Also, storing a reference in a class is often (not always) a mistake. You probably want a value, or possibly a pointer.

Yes, but it might have a negative impact on performance, if the collection is large, and the function is called often. What's wrong with just returning a vector<int> const& (and declaring getValues() const)?

Also, I'm wondering about the fact that your member is a reference. Members should rarely be references.

public:    
    vector<int> getValues(){
        return values;
    }
private: 
    vector <int>& values;

Cannot possibly work as is, what is the reference to your vector actually referencing? Unless you're not showing all code here, it's not gonna work.

Just have a vector<int> values; instead.

Yes, you can do that, but this is not necessarily what you want.

By doing this, your getValues method will make a copy of the vector. This will take some time (depending on the size of the vector).

If you are sure that the vector is not frequently changed, why not return a const reference, like this:

const vector<int> &getValues() {return values;}

return a pair of const_iterators, then the callee is abstracted from the underlying container too...

e.g.

   typedef std::vector<int> vector_type;
public:
   typedef std::pair<vector_type::const_iterator, vector_type::const_iterator> range;

   range getValues() const
   {
     return range(values.begin(), values.end());
   }
private:
   vector_type values;