Ruby variable scope

Thu, 23 Apr 2026 07:25:09 +0000

Ruby has a peculiarity: when you define a variable in a conditional expression (if / unless / case / :? (ternary if)), it becomes visible from then on. It’s as if it was assigned nil before the conditional expression, and you don’t need to explicitly declare it:

a = nil # in this case it is unnecessary
if true
  a = 42
end
puts a.inspect # 42

But if you define a variable in a block, it is defined in the local scope and is no longer visible outside the block, for example:

VariableDefenition on Artem Yegorov

Ruby variable scope