How to break out from a ruby block

Question

Here is Bar do things   class Bar      def do things     Foo some method x  do  x        y   x do something       return y is bad if y bad    how do i tell it to stop and return do things         y do something else     end     keep doing more things   end end   And here is Foo some method    class Foo   def self some method targets   amp block      targets each do  target        begin         r   yield target        rescue          failed  lt  lt  target       end     end   end end   I thought about using raise  but I am trying to make it generic  so I don t want to put anything any specific in Foo

User · Answer

Perhaps you can use the built-in methods for finding particular items in an Array, instead of each-ing targets and doing everything by hand. A few examples:

class Array
  def first_frog
    detect {|i| i =~ /frog/ }
  end

  def last_frog
    select {|i| i =~ /frog/ }.last
  end
end

p ["dog", "cat", "godzilla", "dogfrog", "woot", "catfrog"].first_frog
# => "dogfrog"
p ["hats", "coats"].first_frog
# => nil
p ["houses", "frogcars", "bottles", "superfrogs"].last_frog
# => "superfrogs"

One example would be doing something like this:

class Bar
  def do_things
    Foo.some_method(x) do |i|
      # only valid `targets` here, yay.
    end
  end
end

class Foo
  def self.failed
    @failed ||= []
  end

  def self.some_method(targets, &block)
    targets.reject {|t| t.do_something.bad? }.each(&block)
  end
end

User · Answer

Use the keyword  next  If you do not want to continue to the next item  use break   When next is used within a block  it causes the block to exit immediately  returning control to the iterator method  which may then begin a new iteration by invoking the block again   f each do  line                 Iterate over the lines in file f   next if line 0 1              If this line is a comment  go to the next   puts eval line  end   When used in a block  break transfers control out of the block  out of the iterator that invoked the block  and to the first expression following the invocation of the iterator   f each do  line                Iterate over the lines in file f   break if line     quit n     If this break statement is executed      puts eval line  end puts  Good bye                    then control is transferred here   And finally  the usage of return in a block   return always causes the enclosing method to return  regardless of how deeply nested within blocks it is  except in the case of lambdas    def find array  target    array each with index do  element index      return index if  element    target     return from find   end   nil    If we didn t find the element  return nil end

User · Answer

next and break seem to do the correct thing in this simplified example   class Bar   def self do things       Foo some method 1  10  do  x              next if x    2             break if x    9             print    x          end   end end  class Foo     def self some method targets   amp block        targets each do  target          begin           r   yield target          rescue    gt  x           puts  rescue   x           end      end    end end  Bar do things   output  1 3 4 5 6 7 8

User · Answer

use the keyword break instead of return

User · Answer

To break out from a ruby block simply use return keyword  return if value nil

User · Answer

I wanted to just be able to break out of a block - sort of like a forward goto  not really related to a loop   In fact  I want to break of of a block that is in a loop without terminating the loop   To do that  I made the block a one-iteration loop   for b in 1  2 do     puts b     begin         puts  want this to run          break         puts  but not this      end while false     puts  also want this to run  end   Hope this helps the next googler that lands here based on the subject line

User · Answer

If you want your block to return a useful value  e g  when using  map   inject  etc    next and break also accept an argument   Consider the following   def contrived example numbers    numbers inject 0  do  count  x      if x   3    0       count   2     elsif x odd        count   1     else        count     end   end end   The equivalent using next   def contrived example numbers    numbers inject 0  do  count  x      next count if x even      next  count   2  if x   3    0     count   1   end end   Of course  you could always extract the logic needed into a method and call that from inside your block   def contrived example numbers    numbers inject 0     count  x  count   extracted logic x    end  def extracted logic x    return 0 if x even    return 2 if x   3    0   1 end

[ruby] How to break out from a ruby block?

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