The Ruby Way: Solutions and Techniques in Ruby Programming, Second Edition

5.16. Coercing Numeric Values

Coercion can be thought of as another form of implicit conversion. When a method (+ for example) is passed an argument it doesn’t understand, it tries to coerce the receiver and the argument to compatible types and then do the addition based on those types. The pattern for using coerce in a class you write is straightforward:

class MyNumberSystem

def +(other)
   if other.kind_of?(MyNumberSystem)
     result = some_calculation_between_self_and_other
     MyNumberSystem.new(result)
   else
     n1, n2 = other.coerce(self)
     n1 + n2
   end
 end

end

The value returned by coerce is a two-element array containing its argument and its receiver converted to compatible types.

In this example, we’re relying on the type of our argument to perform some ...