Rails - Jul 2006 - DRY version of RoR book PAYMENT_TYPES example

In the book there is an example how to convert DB payment value to more 
readable from. PAYMENT_TYPES array is defined and then in your views you 
can use it as Order::PAYMENT_TYPES.

The problem is: how should I convert DB values (for example with type 
char(1)) to full string representation. I know that I can add a Hash to 
a model: IM = {''S'' => ''Skype'',
''A'' => ''AIM''}, and in views call it:
<%=
User::IM[user.communicator] %>. But I would be more DRY if in views you 
could use: <%= user.communicator_to_m %>.

This shouldn''t be difficult to implement:
- add Hash to a model: FIELDNAME_TYPES =
[[''S'',''Skype''],[''A'',''AIM'']]
- create additional methods like fieldname_to_m which will get a value 
and convert  it to human readable form using model''s array/hash

Before I try to hack RoR I would like to get some feedback to learn if 
above approach is good. Maybe the problem is already solved in a 
different way or there is a plug-in which implement that idea.

Regards,

-- 
Posted via http://www.ruby-forum.com/.

Hi --

On Wed, 12 Jul 2006, Grzegorz Daniluk wrote:
> In the book there is an example how to convert DB payment value to more
> readable from. PAYMENT_TYPES array is defined and then in your views you
> can use it as Order::PAYMENT_TYPES.
>
> The problem is: how should I convert DB values (for example with type
> char(1)) to full string representation. I know that I can add a Hash to
> a model: IM = {''S'' => ''Skype'',
''A'' => ''AIM''}, and in views call it:
<%> User::IM[user.communicator] %>. But I would be more DRY if in views
you
> could use: <%= user.communicator_to_m %>.
>
> This shouldn''t be difficult to implement:
> - add Hash to a model: FIELDNAME_TYPES =
[[''S'',''Skype''],[''A'',''AIM'']]
> - create additional methods like fieldname_to_m which will get a value
> and convert  it to human readable form using model''s array/hash
>
> Before I try to hack RoR I would like to get some feedback to learn if
> above approach is good. Maybe the problem is already solved in a
> different way or there is a plug-in which implement that idea.
I''m not sure why calling a method is less repetitive than grabbing a
hash value (which, after all, is also a method-call).  Can you
clarify?


David

-- 
http://www.rubypowerandlight.com => Ruby/Rails training & consultancy
http://www.manning.com/black     => RUBY FOR RAILS, the Ruby book for
                                                     Rails developers
http://dablog.rubypal.com        => D[avid ]A[. ]B[lack''s][ Web]log
dblack@wobblini.net              => me

Grzegorz Daniluk wrote:
> This shouldn''t be difficult to implement:
> - add Hash to a model: FIELDNAME_TYPES =
[[''S'',''Skype''],[''A'',''AIM'']]
> - create additional methods like fieldname_to_m which will get a value 
> and convert  it to human readable form using model''s array/hash
Check out the enumerations_mixin. It lets you say something like:

User.gender = Gender[:Male]

And since the data is in the database you can use it in queries to 
dereference the values on reports, etc. And you can add additional data 
to the model.

http://somethinglearned.com/articles/2005/10/25/announcement-new-rails-plugin

http://svn.protocool.com/rails/plugins/enumerations_mixin/trunk/README_ENUMERATIONS

Matt Griffith
http://mattgriffith.net

-- 
Posted via http://www.ruby-forum.com/.

> I''m not sure why calling a method is less repetitive than grabbing
a
> hash value (which, after all, is also a method-call).  Can you
> clarify?
For example:

<%= Order::PAYMENT_TYPES[order.pay_type] %> ...
<%= Order::DELIVERY_TYPES[order.delivary] %> ...
<%= Order::CREDIT_CARD_TYPES[order.credit_card_type] %>

vs

<%= order.pay_type_to_m %> ...
<%= order.delivary_to_m %> ...
<%= order.credit_card_type_to_m %>

You don''t have to type model and hash names. I think this is less 
repetitive in terms of code to write in views, not in terms of code 
which is executed underneath. That''s all.

-- 
Posted via http://www.ruby-forum.com/.

On Jul 12, 2006, at 4:44 AM, dblack@wobblini.net wrote:
> On Wed, 12 Jul 2006, Grzegorz Daniluk wrote:
>
>> In the book there is an example how to convert DB payment value to  
>> more
>> readable from. PAYMENT_TYPES array is defined and then in your  
>> views you
>> can use it as Order::PAYMENT_TYPES.
>>
>> The problem is: how should I convert DB values (for example with type
>> char(1)) to full string representation. I know that I can add a  
>> Hash to
>> a model: IM = {''S'' => ''Skype'',
''A'' => ''AIM''}, and in views call
>> it: <%>> User::IM[user.communicator] %>. But I would be
more DRY if in
>> views you
>> could use: <%= user.communicator_to_m %>.
>
> I''m not sure why calling a method is less repetitive than grabbing
a
> hash value (which, after all, is also a method-call).  Can you
> clarify?
Because grabbing the hash value violates OO encapsulation by exposing
the internal data structure of the object.

-- 
-- Tom Mornini

> I''m not sure why calling a method is less repetitive than grabbing
a
> hash value (which, after all, is also a method-call).  Can you
> clarify?
What about something like this:

class ActiveRecord::Base
  def lm(arg)
    self.class.const_get(arg.to_s.upcase + "_HASH")[self.send(arg)]
  end
end

and in the model then

class Order < ActiveRecord::Base
  ...
  PAY_TYPE_HASH = { "ch" => "Check",
                    "cc" => "Credit card",
                    "po" => "Purchase order" }
  ...
end

and finally in the view

<%= @order.lm(:pay_type) %>

This is much simpler than adding a new method for every attribute. Any 
other ideas?

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