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Re: "How do you arrive at classes?"

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On 14.01.2015 18:40, Joshua Cranmer 🐧 wrote:
> On 1/13/2015 10:57 PM, ram@zedat.fu-berlin.de (Stefan Ram) wrote:
>>    I tried to answer the question »How do you arrive at
>>    classes?« in the classroom, kind-a stuttering, because
>>    I was not prepared for this question. Now, I am curious:
>>    How would /you/ answer this question?
>
> The shortest answer is "there is no one true way to do this."

Right.

> A longer response:
> The primary point of object-oriented programming is to break the state
> up into a series of objects each responsible for managing its own state.
> Keeping that in mind, a class is a collection of state and its
> manipulators that can be reasoned about independently of the rest of the
> program. As you work through and design the system and its API, classes
> will tend to fall out naturally as things that just make sense to exist.

... if you have some experience.

> A caveat is that ultimately the purpose of design is to produce the most
> maintainable program.

Not always: if it's a one off or there are other goals much more 
important (e.g. performance) then maintainability can be sacrificed with 
good reasons.

> Sometimes, things are so simple that adding
> classes makes the code less, rather than more, maintainable. An example
> is parsers: if you're parsing a complex programming language like Java,
> you'll want to have a distinct Parser class. But if you're parsing
> something as simple as an RFC 822 address string, you'll probably want
> to make it a method. Simple here does not mean lines of code (the latter
> parser is ~500 lines of code and one using the former framework is ~700
> lines of code, both including very copious comments), but is rather the
> utility and reuse of state between methods.

Absolutely agree.

> Another caveat is that there is room for reasonable disagreement: two
> different answers on what are classes in a particular applications can
> both be right.

That hints to that "right" and "wrong" are probably the wrong categories 
to judge a design. :-)

Cheers

	robert


-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/

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Re: "How do you arrive at classes?" Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2015-01-14 11:40 -0600
  Re: "How do you arrive at classes?" Robert Klemme <shortcutter@googlemail.com> - 2015-01-14 20:29 +0100

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