irb - How do I dynamically create a local variable in Ruby?

Question

I am trying to dynamically create local variables in Ruby using eval and mutate the local-variables array. I am doing this in IRB.

eval "t = 2"
local_variables # => [:_]
eval "t"
# => NameError: undefined local variable or method `t' for main:Object
local_variables << "t".to_sym # => [:_, :t]
t
# => NameError: undefined local variable or method `t' for main:Object

Answer 1

You have to synchronize the evaluations with the same binding object. Otherwise, a single evaluation has its own scope.

b = binding
eval("t = 2", b)
eval("local_variables", b) #=> [:t, :b, :_]
eval("t", b) # => 2
b.eval('t') # => 2