BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Difference Builder and Strategy pattern          BorlandTalk.com Forum Index -> Delphi OO design View previous topic :: View next topic   Author Message Hubert Anemaat Guest Posted: Wed Dec 08, 2004 11:21 am    Post subject: Difference Builder and Strategy pattern Hello, What is the difference between Builder and Strategy pattern ? I read that Builder is a creation pattern and Strategy is a behavior pattern. The UML diagrams look the same for me. Are objects creating a bar diagram or a circle diagram from data a Builder pattern or a Strategy pattern ? Thanks, Hubert Anemaat Back to top Peter Morris [Air Softwar Guest Posted: Wed Dec 08, 2004 11:51 am    Post subject: Re: Difference Builder and Strategy pattern A builder will create something for you, whereas a Strategy is more like a virtual/abstract method. For example, if you wanted to release an application for charging customers for shipping goods, but the rules for each customer were so specific that you could never introduce anything generic you would use a strategy. You'd problem declare an interface, and have DLLs in the EXE folder. Each customer would have a setting "Tariff calculator name" = "Basic.dll", the DLL would be loaded, the ITariffCalculator extracted, and then used to calculate charges for that customer. You certainly wouldn't want to re-release the app each time you had a new customer. -- Pete ==== Audio compression components, DIB graphics controls, FastStrings http://www.droopyeyes.com Read or write articles on just about anything http://www.HowToDoThings.com My blog http://blogs.slcdug.org/petermorris/ Back to top Jim Cooper Guest Posted: Wed Dec 08, 2004 12:49 pm    Post subject: Re: Difference Builder and Strategy pattern They are similar. In general though, Strategy is used where you want to apply different algorithms to do the same thing. The classic example is wage vs salary employees - you need different calculations to get the monthly pay for each. By putting the pay calculations in another class than the employee class you also allow changing employee's status. Typically the pay will be surfaced in the employee class though. Builder is somewhat different in that the end product is a complex object that is made of objects of a different class than the algorithm in charge of creating that complex object. Often that complex object is a quite different type at different times (and is often a Composite). Cheers, Jim Cooper _______________________________________________ Jim Cooper [email]jim (AT) falafelsoft (DOT) com[/email] Falafel Software http://www.falafelsoft.com _______________________________________________ Back to top Jim Cooper Guest Posted: Wed Dec 08, 2004 1:21 pm    Post subject: Re: Difference Builder and Strategy pattern It strikes me I may not have been that clear :-) A simple explanation is Strategy is different ways to do the same thing, whereas Builder is the same way to build different things :-) For example, I need to parse a text representation to generate a complex set of objects (customers, products etc). So I'm going to use Builder to do that. I have 3 sets of objects, a reader, a set of builders, and the customers,products etc. Now suppose I later want to parse an XML file and build the customers, products etc structure. I will need a different reader and set of builders. What I might do is use Strategy to determine which reader/builder set to use in which situation. Cheers, Jim Cooper _______________________________________________ Jim Cooper [email]jim (AT) falafelsoft (DOT) com[/email] Falafel Software http://www.falafelsoft.com _______________________________________________ Back to top Charles McAllister Guest Posted: Wed Dec 08, 2004 3:13 pm    Post subject: Re: Difference Builder and Strategy pattern Hubert Anemaat wrote: Quote: Hello, What is the difference between Builder and Strategy pattern ? I read that Builder is a creation pattern and Strategy is a behavior pattern. The UML diagrams look the same for me. Are objects creating a bar diagram or a circle diagram from data a Builder pattern or a Strategy pattern ? Hi Hubert. See the thread "name this pattern game" on 10/21 in this group for examples on the strategy pattern. HTH. Back to top Gerrit Beuze Guest Posted: Thu Dec 09, 2004 7:26 am    Post subject: Re: Difference Builder and Strategy pattern Hi Hubert, In addition to what other already said: Quote: The UML diagrams look the same for me. That is the case with many patterns: the structure (inheritance, uses relations) might be identical but the difference is in their intention. Have a look at Proxy and Adapater: very similar. Quote: Are objects creating a bar diagram or a circle diagram from data a Builder pattern or a Strategy pattern ? That depends: If the client creates the abstracted diagram like this // builder usually does not require backpointer? // as it's fed with everything it needs. Builder := TCircleDiagram.Create; Builder.StartDiagram(); Builder.AddElement(10%, 'A"); Builder.AddElement(15%, 'B"); Builder.AddElement(9%, 'C"); etc. etc Builder.AddTitle('bla'); Builder.AddAxis('X', [0,100]); etc. Builder.EndDiagram(); You're typiclaly using a builder. The client provides the elements / data in a fixed way. The builder determines how & which diagram is build. If you're using a strategy, it's usually a few methods you call, // strategy usually uses back pointer or Memento to // fetch the data and do what it should do. Strategy := TCircleDiagram.Create(Self, Memento); Strategy.Execute; Strategy.Free; Gerrit Beuze ModelMaker Tools Back to top Hubert Anemaat Guest Posted: Thu Dec 09, 2004 10:55 pm    Post subject: Re: Difference Builder and Strategy pattern Thank you all for the information ! Hubert Anemaat "Hubert Anemaat" <hubert (AT) anemaat (DOT) nl> schreef in bericht news:41b6e32c$1 (AT) newsgroups (DOT) borland.com... Quote: Hello, What is the difference between Builder and Strategy pattern ? I read that Builder is a creation pattern and Strategy is a behavior pattern. The UML diagrams look the same for me. Are objects creating a bar diagram or a circle diagram from data a Builder pattern or a Strategy pattern ? 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