Better way to itterate through array

Hi, all.

Just wondering if there is a better dry way to itterate through array.
Here is what I'm trying to accomplish.

Some history:
I have an inventory program, that I'm writing to learn rails. It has
multiple tables, one of the main ones is called parts. Parts has name,
manufacturer, vendor, etc columns.
Manufacturer and vendor columns are just storing ids of records from
tables Manufacturers and Vendors.

What I want to do:
In my "index" view - I'm displaying last 10 parts that were added. Right
now in order to make it more human-friendly I'm substituting Vendor id
which I'm storing in my Parts table for Vendor name which I'm pulling
from Vendors table. Then in my View I'm comparing one the fly my
part.vendor to vendor.id. But that means I have to loop through Vendors
array 10 times. Again considering the amount of data I'm working with -
not a big hit, but what other ways are there to either implement it or
to iterate through arrays.

The only other option I can think of is to do a join when I'm pulling
data in a controller - then MySQL will do all the heavy lifting. But I'm
not sure what will take a greater toll on my system.

Thoughts?
Below are snippets of my code.

Controller:
[code]
class PartsController < ApplicationController
  def index
  @parts = Part.find(:all, :limit =>10)
  @vendors = Vendor.find(:all)
  part_status_type = StatusType.find_by_name("part status").id
  @part_statuses = Status.find_all_by_status_type(part_status_type)

  end
[/code]

View
[code]

<h3>Last ten parts added:</h3>
<table border="0" cellspacing="1" cellpadding="5" bgcolor="#666666">
  <tr bgcolor="#cccccc">
    <th>Name</th>
    <th>Part #</th>
    <th>Vendor</th>
    <th>Vendor #</th>
    <th>Status</th>
    <th>Cost</th>
    <th>QTY</th>
  </tr>
<% @parts.each do |p| %>
  <tr bgcolor="#ffffff">
    <td><%= p.name %></td>
    <td><%= p.id %></td>
    <td>
      <% @vendors.each do |v| %>
      <% if v.id == p.vendor %>
        <%= v.name %>
      <% end %>
      <% end %>
    </td>
    <td><%= p.vendor_specific_id %></td>
    <td>
      <% @part_statuses.each do |s| %>
      <% if s.id == p.part_status %>
        <%= s.name %>
      <% end %>
      <% end %>
    </td>
    <td align="right">$<%= p.cost %></td>
    <td align="right"><%= p.total_quantity.to_i %></td>
<% end %>

[/code]

Hi, all.

Just wondering if there is a better dry way to itterate through array.
Here is what I'm trying to accomplish.

Some history:
I have an inventory program, that I'm writing to learn rails. It has
multiple tables, one of the main ones is called parts. Parts has name,
manufacturer, vendor, etc columns.
Manufacturer and vendor columns are just storing ids of records from
tables Manufacturers and Vendors.

What I want to do:
In my "index" view - I'm displaying last 10 parts that were added. Right
now in order to make it more human-friendly I'm substituting Vendor id
which I'm storing in my Parts table for Vendor name which I'm pulling
from Vendors table. Then in my View I'm comparing one the fly my
part.vendor to vendor.id. But that means I have to loop through Vendors
array 10 times. Again considering the amount of data I'm working with -
not a big hit, but what other ways are there to either implement it or
to iterate through arrays.

Ugh. You could make @hash a vendor indexed by id and then you wouldn't have to do the iterating over it. You'd still be loading all the vendors for nothing/

But why not make part have associations for vendor and manufacturer ?

Then you can do

@parts = Part.find(:all, :limit =>10)

and then in your view
<%= p.vendor.name %>

This will make one query each time to load the vendor, but you can defeat that by getting rails to load the vendors up front (and only those vendors actually used with

Part.find :all, :limit => 10, :include => :vendor

Fred

First, prove it’s a performance issue. If it’s not, then don’t worry about it - it might smell funny but it may not be the most important thing in the world on your plate right now. Premature optimization, yadda yadda

Second, I’m reasonably sure you could do this all in sql code either with a find_by_sql, though I can’t really tell how your tables relate.

Third, Fred’s suggestion is really good.

Finally, investigate page, action, or fragment caching for this. This only needs to be queried when the data changes and chances are good that it changes less than it’s read. Even if this code never gets refactored, at least then you reduce the need to run the logic each time.

HTH!

Frederick Cheung wrote:

Manufacturer and vendor columns are just storing ids of records from
array 10 times. Again considering the amount of data I'm working
with -
not a big hit, but what other ways are there to either implement it or
to iterate through arrays.

Ugh. You could make @hash a vendor indexed by id and then you wouldn't
have to do the iterating over it. You'd still be loading all the
vendors for nothing/

But why not make part have associations for vendor and manufacturer ?

Then you can do

@parts = Part.find(:all, :limit =>10)

and then in your view
<%= p.vendor.name %>

This will make one query each time to load the vendor, but you can
defeat that by getting rails to load the vendors up front (and only
those vendors actually used with

Part.find :all, :limit => 10, :include => :vendor

Fred

Fred, now that I discovered associations I have a new question. Is there
any way to create column name aliases.
Here is what I mean. Below is a snippet from my interchangable_part
migration

class CreateInterchangableParts < ActiveRecord::Migration
  def self.up
    create_table :interchangable_parts do |t|
    t.integer :interchanged_part #this is the part the you want
    t.integer :interchangeable_with_part # can substitute / interchange
with this part

  t.timestamps
  end
  end

  def self.down
    drop_table :interchangable_parts
  end
end

Both of these columns need to refer to part_id in part model. How would
I setup association in Part model since I can't call both of these
columns part_id?

Thanks

Fred, now that I discovered associations I have a new question. Is there
any way to create column name aliases.

the associations take a :foreign_key option that says which column to use instead the default. Some examples at http://www.spacevatican.org/2008/5/6/creating-multiple-associations-with-the-same-table

Before you go any further you should really read up on associations - you'll be creating a massive amount of extra work for yourself if you don't

Fred

Frederick Cheung wrote: