`break` in block 原来`break`拥有跳出所有block的能力

gistfile1.rb

def a(&block)
  puts 'enter a'
  b &block
  puts 'exit a'
end

def b(&block)
  puts 'enter b'
  c &block
  puts 'exit b'
end

def c(&block)
  puts 'enter c'
  d &block
  puts 'exit c'
end

def d(&block)
  puts 'enter d'
  block[]
  puts 'exit d'
end

a do 
  puts 'enter block'
  break
  puts 'exit block'
end

# output:
# enter a
# enter b
# enter c
# enter d
# enter block

参考这里

http://stackoverflow.com/questions/4702211/are-return-and-break-useless-inside-a-ruby-block-when-used-as-a-callback

前面的都不用看

a do
  puts 'center block'
  break # 在这里跳出a的block
  puts 'exit block'
end

puts "hello" # break后其实已经把控制权移交到这里了