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block_vs_method_variable_scope

🔐 Understand Variable Scope in Blocks vs Methods​

Ruby’s blocks and methods handle local variables differently. Blocks are closures that can read and modify variables from the surrounding scope, whereas method definitions introduce a new local scope. Knowing this distinction prevents NameErrors and unintended side effects.

# Block scope shares outer variables
x = 5
3.times do |i|
  x += i
end
puts x  # => 8 (5 + 0 + 1 + 2)

# Method scope is isolated
def update_y
  y = 10
end
update_y
puts defined?(y)  # => nil (y is not accessible here)

# Block parameters shadow outer variables
value = 100
[1, 2, 3].each do |value|
  puts value      # prints 1, 2, 3
end
puts value        # => 100 (outer `value` unchanged)