ruby variable as same object (pointers?)

Question

>> a = 5
=> 5
>> b = a
=> 5
>> b = 4
=> 4
>> a
=> 5

how can I set \'b\' to actually be \'a\' so that in the exa

Answer 1

I'm no Ruby expert. But for a technically crazy kluge...that would only work if you felt like going through eval every time you worked with a variable:

>> a = 5
=> 5
>> b = :a
=> :a
>> eval "#{b} = 4"
=> 4
>> eval "#{a}"
=> 4
>> eval "#{b}"
=> 4

Note that a direct usage of b will still give you :a and you can't use it in expressions that aren't in eval:

>> b
=> :a
>> b + 1
NoMethodError: undefined method `+' for :a:Symbol

...and there are certainly a ton of caveats. Such as that you'd have to capture the binding and pass it around in more complex scenarios...

'pass parameter by reference' in Ruby?

@Paul.s has an answer for if you can change the point of declaration to be a wrapper object, but if you can only control the point of reference then here's a BasicReference class I tried:

class BasicReference
    def initialize(r,b)
        @r = r
        @b = b
        @val = eval "#{@r}", @b
    end

    def val=(rhs)
        @val = eval "#{@r} = #{rhs}", @b
    end

    def val
        @val
    end
end

a = 5

puts "Before basic reference"
puts "   the value of a is #{a}"

b = BasicReference.new(:a, binding)

b.val = 4

puts "After b.val = 4"
puts "   the value of a is #{a}"
puts "   the value of b.val is #{b.val}"

This outputs:

Before basic reference
   the value of a is 5
After b.val = 4
   the value of a is 4
   the value of b.val is 4