Rulebooks as Decorators for Engine

[Richard Pruss]

Hi Joe,

I am looking for a decent idiom for dynamically defining the rules from 

multiple classes into the enginer.

Here is a problem definition, to see if I am even thinking along the right line.

I have a engine into which I assert a data feed - of current prices.

I assert strategies into the engine as facts and I use rules based on price

and strategy object data to to take actions, which are mainly methods in said

strategies.

All pretty neat except for how I load rule, currently rules are loaded as I

mentioned before as eval statements in a common rulebook.

More contained and testable would be to have the def rules in the strategy.

Then I could do something like

engine :engine do |e|
  strat1 = StratergyOne.new(lots of fields)
  strat2 = StratergyOne.new(lots of fields)
strat3 = StratergyTwo.new(lots of fields)

  e.assert strat1
e.assert strat2
e.assert strat3

# the hope is that these would assert the ferrari rules from the strategies to the engine  
 strat1.rules
 strat2.rules
 strat3.rules

loop for price assert and match
  e.match

 etc

- Ric

[Matt Smith]

Hi Ric,

Does passing the engine into the rules method help to solve your problem?

strat1.rules(e)

and then use the engine to create the CommonRulebook and rules from there.

Matt

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[Richard Pruss]

I have not quiet got to the stage where I have a problem.  Just playing with

ideas for the design before I start to refractor it.

I was thinking of passing the engine in the initialise but you right in the rule method is

better contained.

- Ric