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How many responsibility an object should take?

dissip

BigCat

发贴: 240
积分: 60

于 2004-05-24 18:13

How many responsibility should an object take(especially in domain modeling)?
option 1. one object should take only 1 responsibility. It seems to be pure and improve the maintainability of the system.But it will make the system full of fine grained object and make the project difficult to understand both by customer and by newer to the project.

option 2. one object for a real object in reality. that is, one object take many responsibility. it seems the object will soon get bigger and bigger. But it will provide a simple mapping between reality and system which can make the customer directly involved in the project and make all the peoples communication/understanding of the problem better.

what's your opinion?

To live is to fight.

作者	Re:How many responsibility an object should take? [Re:dissip]
guru 发贴: 131 积分: 53	于 2004-05-24 21:25 I think it depends on your project's vision, resource, time etc.

作者	Re:How many responsibility an object should take? [Re:dissip]
floater Java Jedi 总版主发贴: 3233 积分: 421	于 2004-05-24 23:25 object composition. Use relations(generalization & various associations) to break them. In general, I wouldn't go beyond 5. Even within 5, I still find from time to time that I could do better. "Any fool can write code that a computer can understand. Good programmers write code that humans can understand." - Martin Fowler, Refactoring - Improving the Design of Existing Code

作者	Re:How many responsibility an object should take? [Re:dissip]
emarket 亢龙有诲 CJSDN高级会员发贴: 460 积分: 82	于 2004-05-25 00:37 SRP 规定一个 class 只应该有一个responsibility

作者

Re:How many responsibility an object should take? [Re:dissip]

dissip

BigCat

发贴: 240
积分: 60

于 2004-05-25 09:23

Personally I prefer option 2:one object take many responsibility. because as the complexity of software increases, the easyer it can be understood, the better. this approach can establish a evey easy relationship between entities in reality and in software world. this can make business people to get involed in the project easily and make software maintainance and evolution easy. But it seems to have its fatal problem: the object will grow rapidly and become a monolith. this will harm the maintainability at the same time.
Are the problem inherent to this approach, or are there any possible approach that could coordinate them?

by the way, what is SRP?

To live is to fight.

作者	Re:How many responsibility an object should take? [Re:dissip]
dissip BigCat 发贴: 240 积分: 60	于 2004-05-25 09:25 I agree at present option 1 will make the project managable. But i think option 2 will be the ideal approach and the future although it can not solve its problem NOW. To live is to fight.

作者	Re:How many responsibility an object should take? [Re:dissip]
emarket 亢龙有诲 CJSDN高级会员发贴: 460 积分: 82	于 2004-05-25 09:34 SRP:The Single Responsibility Principle Agile design 得原则之一，也是refactoring 得方向 http://www.objectmentor.com/resources/articles/srp

作者

Re:How many responsibility an object should take? [Re:dissip]

dissip

BigCat

发贴: 240
积分: 60

于 2004-05-25 10:43

Thank your, emarket . It seems to be a good site.
I read the article and agreed with SRP that :
a Responsibility("a reason for change”) should be encapsulated in a construct(class in current oo methodology).
But what's the result? the system will be full of small object and make the system fragmentary.
There is a old chinese saying"天下大事，分久必合，合久比分"(I don't know whether it is its original words.)
This approach will break the system into small fragment. although each one is pure enough to be evolved easily, the system's whole is harmed.
What i say here is that,as I think, there need to be some approach that can unite these small constructs to make the system more easy to be understood by all people(business or technical) . there are some approaches now including the AOP,MDA that seems to address some part of the problem. But I think maybe a relatively fundamental different approach should be take.

To live is to fight.

作者	Re:How many responsibility an object should take? [Re:dissip]
floater Java Jedi 总版主发贴: 3233 积分: 421	于 2004-05-25 12:53 small objects are much much better than big combos, although both are awful in quite some cases. We can't get a perfect solution, so we choose the one next to it - small objects. "Any fool can write code that a computer can understand. Good programmers write code that humans can understand." - Martin Fowler, Refactoring - Improving the Design of Existing Code

作者	Re:How many responsibility an object should take? [Re:dissip]
emarket 亢龙有诲 CJSDN高级会员发贴: 460 积分: 82	于 2004-05-25 15:41 dissip wrote: there are some approaches now including the AOP,MDA that seems to address some part of the problem. 把他们搞到一起的方法就是 IOC 了 http://martinfowler.com/articles/injection.html

作者

Re:How many responsibility an object should take? [Re:dissip]

dissip

BigCat

发贴: 240
积分: 60

于 2004-05-26 12:25

Agree with floater

As for IOC, it is a way to separating service configuration from the use of services. It does helps to link different object/component together. But it is only at implementation level and will not help to make the system clear CONCEPTUALLY.

I have some ideas about it and i will publish it after i finished it. and i hope you could share your thought then.
thanks

To live is to fight.

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