Question

I’ve been messing around with Ruby (Ruby 1.9.3, IRB 0.9.6(09/06/30)) and I’m trying to develop a complex number class. I have the initialize and to_s methods working fine. I’m now trying to overload the four arithmetic operators.

What I had is the following:

def +(other)
    return ComplexNumber.new(@real + other.@real, @imag + other.@imag)
end

but for some reason it didn’t like other.@real; it says

syntax error: unexpected tIVAR

and points to the comma after other.@real.

So then I changed it to:

def get_values
    return [@real, @imag]
end

def +(other)
    other_values = other.get_values
    return ComplexNumber.new(@real + other_values[0], @imag + other_values[1])
end

Although this works, I have a feeling that it’s not the correct way to do it. I don’t really want to expose the get_values method; isn’t there some way I can access a variable of another instance of the same class?

Answer 1

Instance variables are accessed without the @ when referring to another instance:

other.real

(Assuming you’re either using attr_accessor to define them, or are providing your own accessors. Even within the same instance you may prefer to use the accessors in case there’s logic beyond simply returning the instance variable.)