Oh also, can anyone recommend a really well designed OS application I can
take a look at and study the code?
On Thursday, 16 October 2014 22:19:32 UTC+1, Tom Oram wrote:
>
> Hello Clojure people,
>
> First up, apologies because this is going to be a long message. Howver, if
> you do have the time to read and respond, then I would be extremely
> grateful!
>
> Recently I've decided to give Clojure a proper go. Over the past year or
> so I've paid it a bit of attention: I've read books all about how to use it
> and I've spent a bit of time working through tutorials to create little web
> apps and so on. I understand the language (although not to any great depth
> yet), but I'm still unsure about the best approaches to actually working
> with it.
>
> I've got many years of OOP experience, and I'm a big fan of principles
> like SOLID and approaches like DDD. What I want to do now is, try and learn
> how to build well designed models using Clojure, while using best
> practices! I've started having a bit of a crack at it by building a simple
> app, but I'm finding myself trying to transfer a lot of my existing OOP
> techniques into Clojure. It's working, but I'm wandering if I'm overdoing
> it or perhaps just not doing things "the Clojure way".
>
> So, my very first question is are there any good books or resources on
> modelling, application architecture or best practices, using Clojure?
>
> Next up, maps vs records. I've read that the typical approach is to use
> maps until the design starts to solidify and then you can move to records.
> Is the the general attitude of Clojure developers or do some like to dive
> straight in with records?
>
> The next question is encapsulation: I've taken the approach that I'm kind
> of using namespaces like classes. If I want to create customer entity I
> create a namespace for it, then add a "make" function to it which returns a
> map of the right "shape". I'm then shying away from accessing the map
> directly, and rather doing it through other methods in the namespace which
> take the instance as a parameter. E.g.
>
> (ns app.domain.customer)
>
>
> (defn make [name, email]
> {:name name
> :email email})
>
>
> (defn get-name [customer]
> (:name customer))
>
> Is this a reasonable approach? If not, what might be a better one?
>
> This leads on to safety and defensive programming. Using the approach
> above, how much "type safety" is required? Obviously, in any API which is
> going to be used by other programmers, you've got to handle bad inputs
> well. But what is the Clojure approach in the "domain model"? Coming from
> the DDD mindset, where models are designed to be un-breakable, part of me
> wants to use records for all entities and typehint for them everywhere.
> However, I wander if the Clojure way is more about rigorous testing to make
> sure the wrong values don't get put in in the first place? Also, what about
> libraries like https://github.com/Prismatic/schema, this could be used in
> :pre conditions to be more explicit, is that a common thing?
>
> Next up, how far do you go with creating "types" vs using primitives?
> Again, referring back to DDD, both the email and the name in the example
> above are suitable candidates for value objects. In Clojure, would you
> consider hiding the data behind a set of specialised functions to create,
> access and use it? Or would you just pass the primitive
> string/map/vector/whatever about and work on it directly? Example:
>
>
> ; Given
> (defn make-customer [name email]
> {:name name, :email email})
>
> ; Examples
>
> (def customer1 (make-customer "Tom" "[email protected]"))
>
> ; vs...
>
> (defn make-name [name] name)
>
> (defn make-email [email] email)
>
> (def customer2
> (make-customer (make-name "Tom")
> (make-email "[email protected]")))
>
>
>
> I think that's all I want to ask about now. I do have other questions
> about dependency inversions, but I'll leave that for another time. If
> you've read this far then thank you very very much! Also,I know that no one
> really wants to just sit and read though random peoples code, but, if you
> are interested in my (very very early stages) experimental project, then
> I've put in on https://github.com/tomphp/clojure-cocktails - any
> comments, critiques, PRs or questions would be really great!
>
> Thanks you so much for your times and I look forward to any thoughts or
> suggestions!
> Tom
>
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