[lnkForumImage]
TotalShareware - Download Free Software
Confronta i prezzi di migliaia di prodotti.
Asp Forum
 Home | Login | Register | Search 


 

Forums >

comp.lang.ruby

Using a result as a constant object?

Phy Prabab

10/18/2008 9:11:00 PM

Hello,

I am trying to understand how I can use a return from a method as a constant name for a class. What I am trying to do is take a return I find in a db table and use that name as a class name so that I can use activerecord. I admit my understanding of ActiveRecord is extremely immature so perhaps I am using it wrong.
...
perMatrtix = subMatrix.find[:space].to.upcase

class perMatrix < ActiveRecord::Base; end

blah, blah, blah...

So the return of the find, which is a name (turn to upper) as the name of a class so that I can access that table within the database.

Any help is greatly appreciated! Cheers,
Phy

__________________________________________________
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around
http://mail...

6 Answers

Tim Hunter

10/18/2008 9:54:00 PM

0

Phy Prabab wrote:
> Hello,
>
> I am trying to understand how I can use a return from a method as a constant name for a class. What I am trying to do is take a return I find in a db table and use that name as a class name so that I can use activerecord. I admit my understanding of ActiveRecord is extremely immature so perhaps I am using it wrong.
> ...
> perMatrtix = subMatrix.find[:space].to.upcase
>
> class perMatrix < ActiveRecord::Base; end
>
> blah, blah, blah...
>
> So the return of the find, which is a name (turn to upper) as the name of a class so that I can access that table within the database.
>

If you're getting the class name at run-time how would you write code
that uses class after you've created it? I mean, you can't type the
class name into your program now, you don't know what it is?

I suspect that what you really want to do is simply create a class and
assign the result to a variable. Check out Class.new.

my_class = Class.new(ActiveRecord::Base)
my_inst = my_class.new




--
RMagick: http://rmagick.ruby...

Artem Voroztsov

10/19/2008 8:28:00 AM

0

2008/10/19 Tim Hunter <TimHunter@nc.rr.com>:
> Phy Prabab wrote:
>>
>> Hello,
>>
>> I am trying to understand how I can use a return from a method as a
>> constant name for a class. What I am trying to do is take a return I find
>> in a db table and use that name as a class name so that I can use
>> activerecord. I admit my understanding of ActiveRecord is extremely
>> immature so perhaps I am using it wrong.
>> ...
>> perMatrtix = subMatrix.find[:space].to.upcase
>>
>> class perMatrix < ActiveRecord::Base; end
>>
>> blah, blah, blah...
>>
>> So the return of the find, which is a name (turn to upper) as the name of
>> a class so that I can access that table within the database.
>>
>
> If you're getting the class name at run-time how would you write code that
> uses class after you've created it? I mean, you can't type the class name
> into your program now, you don't know what it is?
>
> I suspect that what you really want to do is simply create a class and
> assign the result to a variable. Check out Class.new.
>
> my_class = Class.new(ActiveRecord::Base)
> my_inst = my_class.new
>
>
>
>
> --
> RMagick: http://rmagick.ruby...
>
>

my_class = Class.new(ActiveRecord::Base) { set_table_name
subMatrix.find[:space].underscore.pluralize }
my_inst = my_class.new

Artem

PS:
Expression "subMatrix.find[:space]" seems strange for me. What is it about?

Sjoerd Andringa

10/19/2008 10:05:00 AM

0

If the ActiveRecord model already exists you can just call constantize
on the string containing the model name:

class SomeModel < ActiveRecord::Base; end

model_name = "SomeModel" # or in your case fetch this from a database
ar_model = model_name.constantize
ar.model.find(120)
--
Posted via http://www.ruby-....

Sjoerd Andringa

10/19/2008 10:05:00 AM

0

Sjoerd Andringa wrote:
> ar.model.find(120)
Should be: ar_model.find(120)
--
Posted via http://www.ruby-....

Sjoerd Andringa

10/19/2008 10:09:00 AM

0

Sjoerd Andringa wrote:
> Sjoerd Andringa wrote:
>> ar.model.find(120)
> Should be: ar_model.find(120)

Be aware that 'constantize' is a method added by ActiveSupport, no
problem if you're using Rails, but you need to require it manually
otherwise.
--
Posted via http://www.ruby-....

Brian Candler

10/19/2008 5:03:00 PM

0

Phy Prabab wrote:
> I am trying to understand how I can use a return from a method as a
> constant name for a class.

def get_name
"Foo"
end

n = get_name
c = Class.new(ActiveRecord::Base) # superclass
Object.const_set(n, c)
--
Posted via http://www.ruby-....