'pass parameter by reference' in Ruby?
You can accomplish this by explicitly passing in the current binding:
def func(x, bdg) eval "#{x} += 1", bdgenda = 5func(:a, binding)puts a # => 6
Ruby doesn't support "pass by reference" at all. Everything is an object and the references to those objects are always passed by value. Actually, in your example you are passing a copy of the reference to the Fixnum Object by value.
The problem with the your code is, that x += 1 doesn't modify the passed Fixnum Object but instead creates a completely new and independent object.
I think, Java programmers would call Fixnum objects immutable.
In Ruby you can't pass parameters by reference. For your example, you would have to return the new value and assign it to the variable a or create a new class that contains the value and pass an instance of this class around. Example:
class Containerattr_accessor :value def initialize value @value = value endenddef func(x) x.value += 1enda = Container.new(5)func(a)puts a.value