Forum: Ruby on Rails Best practice to handle this

Hi!

I have a model which has a field that can have three values only. I 
store
the value in the database as an integer, 0, 1 or 2, but when I display 
it I
want a more appropriate text. And, I want it to be translatable using 
i18n.

Let's say that it corresponds to how difficult something is. So, 0
represents "Easy", 1 represents "Normal" and 2 represents "Hard".
What I did was first to define it as a hash like this:
DIFFICULTIES = { "Easy" => 0, "Normal" => 1, "Hard" => 2 }
Then I can easily pass this to, for instance, simple_form and it will
generate a nice dropdown with the correct values.

But let's say that I have the value and want to display the text. Then 
I'd
have to iterate over the hash to find which key corresponds to the right
value. Right? Not that big of an issue when there are three values as in
this example, but there could be more.

How do you normally handle these cases? Is there any "best practice" to
handle this in an efficient manner?

Cheers,
Linus

On Sat, Jan 26, 2013 at 8:58 PM, Linus Pettersson <
linus.pettersson@gmail.com> wrote:

> Then I can easily pass this to, for instance, simple_form and it will
> generate a nice dropdown with the correct values.
>
> But let's say that I have the value and want to display the text. Then I'd
> have to iterate over the hash to find which key corresponds to the right
> value. Right? Not that big of an issue when there are three values as in
> this example, but there could be more.
>

Use http://www.ruby-doc.org/core-1.9.3/Hash.html#method-i-key to get the
key you want
given a value.

I'm thinking that you will only do this if you have a small number of
constants that you want
to define.  If it is a long list, then use the database for that.


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--

On 01/26, Linus Pettersson wrote:
> Then I can easily pass this to, for instance, simple_form and it will
> generate a nice dropdown with the correct values.
>
> But let's say that I have the value and want to display the text. Then I'd
> have to iterate over the hash to find which key corresponds to the right
> value. Right? Not that big of an issue when there are three values as in
> this example, but there could be more.

I don't know of any best practice for this, but searching in a hash
takes, on average, O(1); so I don't think there's anything to worry
about here. Of course, if the hash gets big you might end up with
maintainability issues, but that's another story.

On Sat, Jan 26, 2013 at 6:58 AM, Linus Pettersson
<linus.pettersson@gmail.com> wrote:
>
> But let's say that I have the value and want to display the text. Then I'd
> have to iterate over the hash to find which key corresponds to the right
> value. Right? Not that big of an issue when there are three values as in
> this example, but there could be more.
>
> How do you normally handle these cases? Is there any "best practice" to
> handle this in an efficient manner?

Not quite sure if I understand this entirely, but you're looking to be
able to output the associated text in some place *other* than
simple_form? (i.e., when you're displaying the record?)

Seems like it should be straight-forward to map them to values in your
locale file. no?

en:
  difficulties:
    0: Easy
    1: Normal
    2: Hard

then just invoke:

  t 'difficulties.#{difficulty}'

where you want to display it? And maybe use this to build the Hash for
simple_form to begin with?

Hey,
      You can have constants defined in a file called constants.rb in 
your
initializers folder.

DIFFICULTIES = { "Easy" => 0, "Normal" => 1, "Hard" => 2 ,
0=>"Easy",1=>"Normal", 2=>"Hard"}

This will help you to get your values both ways easily.