Question

Why doesn’t this code work?

b if b = true

Error: undefined local variable or method `b'

But this does:

if b = true
    b
end

Shouldn’t they be the same?

Answer 1

This is a very good question. It has to do with the scoping of variables in Ruby.

Here is a post by Matz on the Ruby bug tracker about this:

local variable scope determined up to down, left to right. So a local variable first assigned in the condition of if modifier is not effective in the left side if body. It’s a spec.