Interpretation as a local variable overrides method name?

Question

As in this question, when a local variable not defined is used within its own assignment, it is evaluated to nil.

x = x # => nil 
         


        

Answer 1

I think in your case it's because it's what's expected :P

1.9.3-p194 :001 > {}.instance_eval{a=1}
 => 1 
1.9.3-p194 :002 > {}.instance_eval{a}     
NameError: undefined local variable or method `a' for {}:Hash
    from (irb):2:in `block in irb_binding'
    from (irb):2:in `instance_eval'
    from (irb):2
    from /Users/rafael/.rvm/rubies/ruby-1.9.3-p194/bin/irb:16:in `
'

Instance eval evaluates code at instance level so each hash you are declaring is different. If you want to return keys this works

1.9.3-p194 :003 > {}.instance_eval{keys = self.keys
1.9.3-p194 :004?>   keys = keys}
 => []