Call next for outer loop from within a method

Question

Is it possible to call next from within a method for an outer loop:

bot.rb

while Option.daemon_active?(daemon: "bot")
  .....
  Trade.market_order
  ....
end

trade.rb

class Trade
  def self.market_order
     ... complex code ...
     response = exchange.market_sell
     next if response["state"] == false # This fails. This should start new iteration of while in bot.rb
  end
end

There is quite similar question, but it doesn't seem to suit me: call next on ruby loop from external method

What’s wrong with `next unless Trade.market_order` in the while block? — Aleksei Matiushkin, Apr 21 '15 at 10:02
agreed with @mudasobwa the `Bot` should not be controlled via `Trade`, it is simply not its responsibility and increases coupling which usually should be avoided (hard to follow path of execution, hard to refactor, `Trade` may break if `Bot` changes etc.) — jethroo, Apr 21 '15 at 10:07
Thank you @mudasobwa. Good comment, although right now market order is much more complicated than I shown here, there are lot of checks and all of them need to call next at some point. Maybe I need to simplify it — Ilya Cherevkov, Apr 21 '15 at 10:11
`return false` everywhere you need the next iteration or use @sawa’s approach with `catch`. — Aleksei Matiushkin, Apr 21 '15 at 10:12

score 3 · Accepted Answer · answered Apr 21 '15 at 10:04

3

Yes. You should use throw and catch.

bot.rb

while Option.daemon_active?(daemon: "bot")
  catch(:foo) do
    ...
    Trade.market_order
    ...
  end
end

trade.rb

class Trade
  def self.market_order
    ...
    response = exchange.market_sell
    throw :foo if response["state"] == false
  end
end

answered Apr 21 '15 at 10:04

sawa

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2

It seems you are overdesigned this. `response["state"] ? response : nil` as a return value from `market_order` and `next unless market_order` do the trick in a way more readable manner. – Aleksei Matiushkin Apr 21 '15 at 10:06
@mudasobwa That is not equivalent to the OP's code. `false` and `nil` are different. – sawa Apr 21 '15 at 10:08
Occasionally it is. OMG. `response["state"] != false ? response : false`. – Aleksei Matiushkin Apr 21 '15 at 10:08
`next unless market_order` may work, but that is not what OP asked. I agree with you that this may be an XY-question. – sawa Apr 21 '15 at 10:10
This is exactly what OP asked. Furthermore, this is exactly what your code does. – Aleksei Matiushkin Apr 21 '15 at 10:11

Call next for outer loop from within a method

1 Answers1