Object reference vs Void return type for a Method

Question

I was looking at some open source source code and I noticed that for some methods, rather than using void for a return type, they had used a reference to that class.

Example:

class Object
{
private:
    float m_x;
public:
    Object();
    Object& setX(float x)
    {
        m_x = x;
        return *this;
    }
};

Normally, I would write the same function like this:

class Object
{
private:
    float m_x;
public:
    Object();
    void setX(float x)
    {
        m_x = x;
    }
};

Is there any advantage of using one over the other?

Answer 1

Yes, there are some advantages with returning a reference. When returning a reference you can keep on working on the returned reference and chain multiple function calls together. For example if there were a setY function too, you could do this:

object.setX(5).setY(10);

Returning a reference doesn't really have disadvantages but allows some nice things. It can be used to create fluent interfaces, workaround the lack of named parameters in C++ if you want, and other things.

Related reads:

• What does object.method1().method2() mean?
• What is the “Named Parameter Idiom”?
• What's a fluent interface?
• Fluent interface