Kernel#local_variables

local_variables -> [symbol]

The local_variables method returns an array of all local variable names defined in the current scope. It’s useful for debugging, metaprogramming, and understanding variable scope.

Basic Usage

# In current scope
name = "Alice"
age = 30
city = "NYC"

puts local_variables  # => [:name, :age, :city]

Practical Examples

Debugging

def inspect_locals
  puts "Local variables: #{local_variables.inspect}"
end

name = "test"
inspect_locals  # Shows: [:name]

Dynamic Variable Handling

# Set variables dynamically
local_variables.each do |var|
  value = binding.local_variable_get(var)
  puts "#{var} = #{value}"
end

Scope Inspection

x = 1
y = 2

def method_with_own_scope
  z = 3
  puts local_variables  # Only shows :z
end

method_with_own_scope
puts local_variables  # Shows :x, :y

Variable Capture

def capture_variables
  captured = {}
  local_variables.each do |var|
    captured[var] = binding.local_variable_get(var)
  end
  captured
end

name = "Alice"
age = 30
capture_variables  # => {:name=>"Alice", :age=>30}

Within Blocks

# Blocks create new scope for local variables
x = 10
local_variables  # => [:x]

3.times do |i|
  y = i
end

# y not visible here (different scope)
puts local_variables  # => [:x]

Conditional Variables

if false
  secret = "hidden"
end

puts local_variables  # [:secret] - variable exists but is nil!

Debugging Helpers

def debug_locals
  local_variables.each do |var|
    value = binding.local_variable_get(var)
    puts "#{var.inspect}: #{value.inspect}"
  end
end

Binding Integration

# Use with Binding objects
b = binding
x = 5
puts b.local_variables  # => [:x]

# From other scopes
def get_binding
  local_var = "hello"
  binding
end

b = get_binding
puts b.local_variables  # => [:local_var]

Common Use Cases

• Debugging variable states
• Building REPL tools
• Serializing scope
• Dynamic method creation
• Template engines

See Also

• Kernel#caller
• Kernel#eval
• Kernel#format