On another side note:
@Ryan - You wrote:
A more efficient way is to do this is:
@project_names = Project.all(:select => 'name').map(&:name)
While you've made a database optimisation there, you've also used the
shorthand notation for the map function. I read somewhere that map
(&:name) is quite a bit less efficient than map{ |p| p.name }
unfortunately I can't find the article that convinced me in the first
place... I can only find this blog with the issue mentioned in the
comments:
http://blog.hasmanythrough.com/2006/3/7/symbol-to-proc-shorthand
On Dec 27, 2:23 am, Sazima <[email protected]> wrote:
> Zhao,
>
> I think the most straightforward way is using columns.map
> (Project.columns.map { |c| puts c.name }), just like the inspect
> method of ActiveRecord:
>
> inspect()
>
> Returns a string like ‘Post id:integer, title:string, body:text‘
>
> # File vendor/rails/activerecord/lib/active_record/base.rb, line 1348
> 1348: def inspect
> 1349: if self == Base
> 1350: super
> 1351: elsif abstract_class?
> 1352: "#{super}(abstract)"
> 1353: elsif table_exists?
> 1354: attr_list = columns.map { |c| "#{c.name}: #{c.type}" }
> * ', '
> 1355: "#{super}(#{attr_list})"
> 1356: else
> 1357: "#{super}(Table doesn't exist)"
> 1358: end
> 1359: end
>
> Cheers, Sazima
>
> On Dec 26, 3:27 am, Mohit Sindhwani <[email protected]> wrote:
>
> > Zhao Yi wrote:
> > > Ryan wrote:
>
> > >> I think it's been around since Rails 2.1
>
> > >> Project.first
> > >> Project.last
> > >> Project.all
>
> > >> all work.
>
> > > I think the first last and all refers to rows. I want to select columns.
>
> > If I'm not wrong, relational algebra doesn't identify a sequence between
> > the elements of a row, i.e., I don't think it gives you the ability to
> > select a column specifically. That said, you could probe for the schema
> > and get the elements using that - something like how the dynamic
> > scaffold used to work in earlier Rails.
>
> > Cheers,
> > Mohit.
> > 12/26/2008 | 1:27 PM.
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