# frozen_string_literal: true

# sample-frozen-string.rb: what the frozen_string_literal magic comment does.
# Free sample from 99helpers.com/file-types/rb
# Run: ruby sample-frozen-string.rb
# Try it without line 1 too: on Ruby 3.4 and later, `ruby -W:deprecated`
# then warns at step 1 instead of raising, because literals are "chilled".

# 1. With the comment, string literals are frozen: changing one in place
#    raises FrozenError.
greeting = "Hello"
begin
  greeting << ", world"
rescue FrozenError => e
  puts "1. #{e.class}: #{e.message}"
end

# 2. Methods that return a new string still work on frozen strings.
puts "2. #{greeting + ', world'} / #{greeting.upcase} / frozen? #{greeting.frozen?}"

# 3. Unary plus (or dup) gives a mutable copy when you need one.
buffer = +"Hello"
buffer << ", world"
puts "3. #{buffer} / frozen? #{buffer.frozen?}"

# 4. Interpolated strings are never frozen (since Ruby 3.0).
name = "Ada"
puts "4. frozen? #{"Hi #{name}".frozen?}"

# 5. Identical frozen literals are the same object, which saves memory.
puts "5. same object? #{'abc'.equal?('abc')}"