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Rules engine
- 1.
- 3. Rules engine Replacing imperativemodel: ◦commands in sequence with conditionals and loops ◦set of rules – each rule has condition and action
- 4. Rules engine addressthe following issue if car.owner.hasCellPhone then premium += 100; if car.model.theftRating > 4 then premium += 200; if car.owner.livesInDodgyArea && car.model.theftRating > 2 then premium += 300;
- 5. The solution Create a bunch objectswith conditions and actions Store them in a collections Run thought them to evaluate the conditions Execute the actions
- 6.
- 7. What are thebenefits Single Responsibility Principle (SRP) Open/Close Principle (OCP) Liskov substitution principle (LSP) Interface segregation principle Dependency inversion principle
- 10. • Algorithms canbe selected on the fly Strategy pattern • Combinable business logic in a Boolean fashion Specification pattern • Command objects are handled or passed on to other objects by logic-containing processing object Chain of responsibility pattern
- 12.
Editor's Notes
- #2 Short introduction to me and the topic.
- #3 Why we use design patterns? Have you ever used design patterns? Last used design patterns? http://www.codeproject.com/Tips/808058/Reasons-for-using-design-patterns
- #4 http://martinfowler.com/bliki/RulesEngine.html http://martinfowler.com/dslCatalog/productionRule.html http://www.michael-whelan.net/rules-design-pattern/
- #6 https://github.com/mwhelan/Blog_RulesPattern/tree/master/src/RulesPattern
- #8 How many of you have heard about SOLID - SRP, OCP?
- #9 Business rules and validation are an integral part of most business applications. There are rules and validations that must occur during processing of business logic. Most applications will combine the business logic with rules and data validation – when this happens, testing and maintaining applications becomes more difficult.
- #11 The Strategy Pattern defines a family of algorithms, encapsulates each one, and makes them interchangeable. Strategy lets the algorithm vary independently from clients that use it. (http://csharpbytes.azurewebsites.net/the-strategy-pattern/) The Specification Pattern outlines a business rule that is combinable with other business rules. In this pattern, a unit of business logic inherits its functionality from the abstract aggregate Composite Specification class. The Composite Specification class has one function called IsSatisfiedBy that returns a boolean value. After instantiation, the specification is "chained" with other specifications, making new specifications easily maintainable, yet highly customizable business logic. Furthermore, upon instantiation the business logic may, through method invocation or inversion of control, have its state altered in order to become a delegate of other classes such as a persistence repository. (https://en.wikipedia.org/wiki/Specification_pattern, http://www.ilove-it.com/post/2016/06/17/using-the-specification-pattern-in-typescript) http://www.oodesign.com/chain-of-responsibility-pattern.html http://stackoverflow.com/questions/5039024/whats-the-difference-between-chain-of-responsibility-and-strategy-patterns