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freezing_constants_to_prevent_mutation

🛡️ Freezing Constants to Prevent Mutation​

Constants can hold mutable objects like arrays or hashes. To avoid accidental modifications, use #freeze so that attempts to change the object raise an error.

# Without freezing
ROLES = ['admin', 'user']
ROLES << 'guest'
puts ROLES.inspect  # => ["admin", "user", "guest"]

# With freezing
PERMISSIONS = { read: true, write: false }.freeze
PERMISSIONS[:delete] = true
# => RuntimeError: can't modify frozen Hash

# You can also freeze nested objects
SETTINGS = {
  retries: 3,
  backoff: [1, 2, 4]
}.freeze
SETTINGS[:backoff] << 8
# => works unless you freeze the inner array too
SETTINGS[:backoff].freeze
SETTINGS[:backoff] << 8
# => RuntimeError: can't modify frozen Array