Hi Tom
If you are trying to only keep one instance of a particular currency around
•just• for the sake of comparisons, you can remove that need by treating
currency as a value object.
You can define the ==(other) method on your class, and then simple
comparisons of a.currency == b.currency will be true, even when they are
different instances of the same class.
def ==(other)
if other.class == self.class
other.currency_code == self.currency_code
else
super
end
end
(Excuse bad formatting)
Class Variables are fraught with gotchas, especially in tests and hot code
reloading. I've had issues getting stale data on production deploys with
code that uses
Class vars. :(
On Saturday, 2 January 2016, Gareth Townsend <gareth.towns...@me.com> wrote:
> Hi Tom,
>
> Are you using the Money gem? If not, I suggest you check it out.
>
> Gareth Townsend
> http://www.garethtownsend.info
>
> > On 2 Jan 2016, at 19:27, Ravi (Tom) Hale <r...@hale.ee <javascript:;>>
> wrote:
> >
> > Hi all,
> >
> > Me again :) Simon Hildebrandt recommended me to join here as I've been
> largely learning / using Ruby in a vacuum (I'm teaching myself while
> backpacking planet Earth). It's great to have people to ask these questions
> - and well thought-out and clearly written replies coming back.
> >
> > I'm working on a program that deals with currency trading. The Currency
> class keeps track of all instances so that only one instance of (for
> example) :AUD is created. It does this via `private_class_method :new` and
> a class instance Hash of (currency_code => instance) to store already
> created objects.
> >
> > I'm trying to work out how to test this class without the tests being
> order-dependent.
> >
> > I've currently got a spec with:
> > context 'before the first instance is created'
> >
> > This was working just fine until I added some more tests in front of it,
> where currency objects were created.
> >
> > I see a few options:
> > 1) Create a Currency.reset! class method to reset the class to the state
> at BEGIN
> > 2) Somehow reset the Currency class to load time in a more elegant way
> > 3) Get rid of the class variables entirely (and still ensure that only
> object per currency code exists)
> >
> > I'm fudging with 1) for now to keep in the Green. 3 seems to be cleanest
> in terms of textbook OO design, but I can't see how to textbookify this...
> >
> > Any suggestions on how to implement 2, 3 (or 4..)?
> >
> > Cheers,
> > Tom
> >
> > P.S. Let me know if there is a more appropriate forum to ask questions
> such as this
> >
> > --
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--
Garrow Bedrossian
+ 61 401 532 538
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