Loop control with break next and redo

The flow of execution of a Ruby block may be controlled with the break, next, and redo statements.

`break`

The break statement will exit the block immediately. Any remaining instructions in the block will be skipped, and the iteration will end:

actions = %w(run jump swim exit macarena)
index = 0

while index < actions.length
  action = actions[index]

  break if action == "exit"

  index += 1
  puts "Currently doing this action: #{action}"
end

# Currently doing this action: run
# Currently doing this action: jump
# Currently doing this action: swim

`next`

The next statement will return to the top of the block immediately, and proceed with the next iteration. Any remaining instructions in the block will be skipped:

actions = %w(run jump swim rest macarena)
index = 0

while index < actions.length
  action = actions[index]
  index += 1

  next if action == "rest"

  puts "Currently doing this action: #{action}"
end

# Currently doing this action: run
# Currently doing this action: jump
# Currently doing this action: swim
# Currently doing this action: macarena

`redo`

The redo statement will return to the top of the block immediately, and retry the same iteration. Any remaining instructions in the block will be skipped:

actions = %w(run jump swim sleep macarena)
index = 0
repeat_count = 0

while index < actions.length
  action = actions[index]
  puts "Currently doing this action: #{action}"

  if action == "sleep"
    repeat_count += 1
    redo if repeat_count < 3
  end

  index += 1
end

# Currently doing this action: run
# Currently doing this action: jump
# Currently doing this action: swim
# Currently doing this action: sleep
# Currently doing this action: sleep
# Currently doing this action: sleep
# Currently doing this action: macarena

`Enumerable` iteration

In addition to loops, these statements work with Enumerable iteration methods, such as each and map:

[1, 2, 3].each do |item|
  next if item.even?
  puts "Item: #{item}"
end

# Item: 1
# Item: 3

Block result values

In both the break and next statements, a value may be provided, and will be used as a block result value:

even_value = for value in [1, 2, 3]
  break value if value.even?
end

puts "The first even value is: #{even_value}"

# The first even value is: 2

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