Newbie worries with "Developing Rails Applications on Max OSX Leopard"

Rails
#1

Hello There,
As a new comer to RoR, I started to follow the article
http://developer.apple.com/tools/developonrailsleopard.html. In short
you create to entities and one one-to-many relation linking them.

Everything was good until the establishment of the relation. I am
unable to go any further than “Linking Models Together” : I can create
the “vendors” mentionned in the exemple, and I can get an “event” to
look to. But when I try to create an “expense”, I get a message
saying :

event.expenses.create(:vendor => vendor1, :amount => 75.00)
NoMethodError: undefined method expenses' for #<Event:0x125e008> from /Library/Ruby/Gems/1.8/gems/activerecord-2.0.2/lib/active_record/ attribute_methods.rb:205:inmethod_missing’
from (irb):2

Could anybody help me ? I have checked the classes files, everything
seems according to the article. I did checks on the database, the
table “expenses” has been created but is empty. The “id” fiels are
present in each of the tables… I don’t see where to look to now.

Thanks in advance,

Thierry

#2

Thierry wrote:

event.expenses.create(:vendor => vendor1, :amount => 75.00)
NoMethodError: undefined method expenses' for #<Event:0x125e008> from /Library/Ruby/Gems/1.8/gems/activerecord-2.0.2/lib/active_record/ attribute_methods.rb:205:inmethod_missing’
from (irb):2

Could anybody help me ? I have checked the classes files, everything
seems according to the article. I did checks on the database, the
table “expenses” has been created but is empty. The “id” fiels are
present in each of the tables… I don’t see where to look to now.

Do you have the following in your Event class:

has_many :expenses

?
This is the line that give the Event class the method “expenses” which
links to the Expense class. And in the Expense class:

belongs_to :event

to get the map the other way around giving the Expense class the method
“event”.

#3

Thierry

To easily remember what Mark told you, just remember that the foreign
key is always in the model that has the belongs_to relationship… When
I first started playing with AR, that little fact made everything much
more easier to comprehend…

hth

ilan

#4

Mark,

Thanks for your answer. Precisely, it seems to me that I have
everything right. I put the code here :

===== > In the “event.rb” file :

class Event < ActiveRecord::Base
validates_presence_of :name
validates_numericality_of :budget, :greater_than => 0.0

has_many :expenses
has_many :vendors, :through => :expenses

def total_expenses
expenses.sum(:amount) || BigDecimal(“0.0”)
end

def budget_exceeded?
total_expenses > budget
end

end

===> In the expense.rb file :

class Expense < ActiveRecord::Base
belongs_to :event
belongs_to :vendor
end

===> In the vendor.rb file :

class Vendor < ActiveRecord::Base
has_many :expenses
has_many :events, :through => :expenses
end

Thanks again

#5

That’s it :

Expense.column_names
=> [“id”, “event_id”, “vendor_id”, “amount”, “created_at”,
“updated_at”]

Event.column_names
=> [“id”, “name”, “budget”, “created_at”, “updated_at”]

Expense.column_names
=> [“id”, “event_id”, “vendor_id”, “amount”, “created_at”,
“updated_at”]

Vendor.column_names
=> [“id”, “name”, “email”, “created_at”, “updated_at”]

It looks fine too, doesn’t it ?

#6

Thierry wrote:

That’s it :

Expense.column_names
=> [“id”, “event_id”, “vendor_id”, “amount”, “created_at”,
“updated_at”]

Event.column_names
=> [“id”, “name”, “budget”, “created_at”, “updated_at”]

It looks fine too, doesn’t it ?

Yes. Was the error produced in a console that you started after making
the extra changes to the Event and Expense models? In a console, the
models are loaded when first used only and if you change them then you
need to reload them. You can do this with:

reload!

or just by restarting the console (use “quit” to exit, then run the
console again).

#7

Thierry wrote:

Thanks for your answer. Precisely, it seems to me that I have
everything right. I put the code here :

That looks fine. Can you post the results of running (in the
application console):

Event.column_names

and:

Expense.column_names

Just to confirm that these two models are both set up correctly too…

#8

I did it as follows :

$ script/console
Loading development environment (Rails 2.0.2)

event = Event.find_by_name(‘Bienvenue’)
=> #<Event id: 4, name: “Bienvenue”, budget: #<BigDecimal:
125d57c,‘0.456E3’,4(8)>, created_at: “2008-03-05 17:33:11”,
updated_at: “2008-03-05 17:33:11”>

event.expenses.create(:vendor => vendor1, :amount => 75.00)
NoMethodError: undefined method expenses' for #<Event:0x125dd88> from /Library/Ruby/Gems/1.8/gems/activerecord-2.0.2/lib/active_record/ attribute_methods.rb:205:inmethod_missing’
from (irb):2

I am really lost…

#9

SOLVED

In fact, I have been fooled by XCode that does not save the files when
it tells you that it does… I had to close completely XCode for some
modifications to be taken into account by rails. I have noticed this
when I had to restart my computer (battery low), my files where in an
old version. When I retyped the missing code I made typos, and I saw
them appear in the logs. The only solution to correct them has been to
close completely XCode and to execute a reload! in the console… A
bit strange.
Thanks to all and sorry for your time,

Thierry

#10

I had this exact same problem. Found this page searching for a
solution to my “NoMethodError” blues. Had to close XCode and re-open
it for the changes to be recognized. That is a VERY annoying
problem.

Also had to quit the ruby console and restart it. Using the “reload!”
command mentioned above did not work.

#11

Sorry if this is post is in the wrong place. I am a ROR newbie also
working thru the “Developing Rails Applications on Max OSX Leopard”
article. I am having a separate issue though.
I’m wondering if my version (Rails 2.1.1) differs from that in the
tutorial(2.0.2) in the way it returns a sum:

Tutorial:

event.expenses.sum(:amount)
=> #BigDecimal:1a04960,‘0.1E3’,4(8)

When I run this expression returns:

event.expenses.sum(:amount)
=> 200

Later when running unit tests:

require ‘test_helper’

class EventTest < ActiveSupport::TestCase
def test_budget
event = Event.new(:name => ‘Test Event’, :budget => 30.00)
event.expenses.build(:amount => 10.00)
event.expenses.build(:amount => 20.50)
assert event.save

assert_equal BigDecimal("30.50"), event.total_expenses
assert event.budget_exceeded?

end
end

I get the following failure:

  1. Failure:
    test_budget(EventTest)
    [./test/unit/event_test.rb:10:in test_budget' /Library/Ruby/Gems/1.8/gems/activesupport-2.1.1/lib/ active_support/testing/setup_and_teardown.rb:33:insend’
    /Library/Ruby/Gems/1.8/gems/activesupport-2.1.1/lib/
    active_support/testing/setup_and_teardown.rb:33:in `run’]:
    <#BigDecimal:213bad0,‘0.305E2’,8(8)> expected but was
    <30.5>.

Are these the result of some casting error?

Thanks.