[LRUG] The advantage of immutability?

[Gerhard Lazu]

Should a Request know or even care about its denial? Which parts of your
app need to know about request denials?

These questions are meant to open up the path to your answer. Simple Design
by Corey Haines will help.

I can only reinforce Roland's point: keep it simple.

Gerhard

On Wednesday, 9 September 2015, Jonathon Horsman <jonathon at arctickiwi.com>
wrote:

> Hey smart people
>
> Can you shed some light on why an immutable object is an advantage for a
> web-based Ruby app?
>
> For example this app I'm working on has these Request things and a user
> has the ability to deny a Request.
>
> So the user would click a button which performs a post to the Request
> controller's deny action.
> If I were using Rails or some non-immutable based system I would fetch the
> object from the database, set it's status to denied, and save it.
>
> However since this Request is an immutable object, I have to either:
>
> 1. Write an update_status method which sets that value in the database,
> which becomes tedious when there's lots of possible attribute update
> combinations
> or
> 2. Read the object from the database, copy all the values to a new object
> with the denied status, and stick that back into the database. Seems like
> pointless overhead and could be dangerous if later that object gets another
> attribute which I forget to copy.
>
> My knowledge of immutable objects originates with Java Strings which I
> understand makes sense for performance and memory management reasons.
> I don't think this applies here though?
>
> Thanks!
>
> Jonno
>


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