Issue with eager loading in nested routes

Hi Everyone,

I have issue while doing eager loading when url is =>
http://127.0.0.1:3001/projects/1/features
I also did <%= debug @features %> to dump @feature object but I did
not see ‘owner’ being eager-loaded.

Can anyone find out why owner is not being ‘eager-loaded’?

Thanks in advance.

========= features_controller.rb -> index method

def index
@project = Project.find(params[:project_id])
@features = @project.features.find(:all, :include =>
[:owner, :project])

respond_to do |format|
  format.html # index.html.erb
  format.xml  { render :xml => @features }
end

end

========= Output of <%= debug @features %>


  • !ruby/object:Feature
    attributes:
    project_id: “1”
    updated_at: 2009-10-24 11:07:19
    created_at: 2009-10-24 11:07:19
    attributes_cache: {}

    project: &id001 !ruby/object:Project
    attributes:
    status: In Progress
    title: TestProject
    id: “1”
    finished_on: 2009-12-31 23:59:00
    owner_user_id: “4”
    brief: RAID Controller and DMA Engine for Invader
    created_at: 2009-10-20 19:35:15
    attributes_cache: {}

  • !ruby/object:Feature
    attributes:
    project_id: “1”
    updated_at: 2009-10-24 11:26:09
    details: for testing
    priority: normal
    id: “3”
    owner_id: “1”
    brief: test feature updated
    created_at: 2009-10-24 11:18:11
    attributes_cache: {}

    project: *id001

========= Error in browser

NoMethodError in Features#index
Showing app/views/features/index.html.erb where line #19 raised:

You have a nil object when you didn’t expect it!
The error occurred while evaluating nil.username

Extracted source (around line #19):

16:

<%=h feature.details %>
17: <%=h feature.priority %>
18: <%=h feature.project.title %>
19: <%=h feature.owner.username %>
20: <%= link_to ‘Show’, [@project, feature] %>
21: <%= link_to ‘Edit’, edit_project_feature_path(@project,
feature) %>
22: <%= link_to ‘Destroy’, [@project, feature], :confirm =>
‘Are you sure?’, :method => :delete %>

========= Server Log

ActionView::TemplateError (You have a nil object when you didn’t
expect it!
The error occurred while evaluating nil.username) on line #19 of app/
views/features/index.html.erb:
16:

<%=h feature.details %>
17: <%=h feature.priority %>
18: <%=h feature.project.title %>
19: <%=h feature.owner.username %>
20: <%= link_to ‘Show’, [@project, feature] %>
21: <%= link_to ‘Edit’, edit_project_feature_path(@project,
feature) %>
22: <%= link_to ‘Destroy’, [@project, feature], :confirm =>
‘Are you sure?’, :method => :delete %>
app/views/features/index.html.erb:19
app/views/features/index.html.erb:13:in `each'
app/views/features/index.html.erb:13
app/controllers/features_controller.rb:8:in `index'
-e:2:in `load'
-e:2

Rendered rescues/_trace (94.0ms)
Rendered rescues/_request_and_response (0.0ms)
Rendering rescues/layout (internal_server_error)

On Oct 24, 1:58 pm, nin_d [email protected] wrote:

Hi Everyone,

I have issue while doing eager loading when url is =>http://127.0.0.1:3001/projects/1/features
I also did <%= debug @features %> to dump @feature object but I did
not see ‘owner’ being eager-loaded.

Can anyone find out why owner is not being ‘eager-loaded’?

Does the owner exist at all ? remove the :include, if the exception
persists then you know eager loading is not at fault.

Fred

Fred, owner do exist.

class Feature < ActiveRecord::Base
belongs_to :project
belongs_to :owner, :class_name => “User”, :foreign_key => “owner_id”
end

Now in features controller, I have

@features = @project.features.find(:all, :include => :owner)

and dump for @features in view is where i see only two features being
loaded and not the corresponding owner (only 1 in this case, with id


  • !ruby/object:Feature
    attributes:
    project_id: “1”
    updated_at: 2009-10-24 11:07:19
    details: Represent Single Source Mode opcode
    priority: nornal
    id: “2”
    owner_id: “1”
    brief: Opcode - SSM
    created_at: 2009-10-24 11:07:19
    attributes_cache: {}

  • !ruby/object:Feature
    attributes:
    project_id: “1”
    updated_at: 2009-10-24 11:26:09
    details: for testing
    priority: normal
    id: “3”
    owner_id: “1”
    brief: test feature updated
    created_at: 2009-10-24 11:18:11
    attributes_cache: {}

Oops I had removed that myself. Damn!

Consider this please -

Now in features controller, I have
@features = @project.features.find(:all, :include => :owner)
and dump for @features in view is where i see only two features being
loaded and not the corresponding owner (only 1 in this case, with id


  • !ruby/object:Feature
    attributes:
    project_id: “1”
    updated_at: 2009-10-24 11:07:19
    details: some crap
    priority: nornal
    id: “2”
    owner_id: “1”
    brief: foo
    created_at: 2009-10-24 11:07:19
    attributes_cache: {}
  • !ruby/object:Feature
    attributes:
    project_id: “1”
    updated_at: 2009-10-24 11:26:09
    details: for testing
    priority: normal
    id: “3”
    owner_id: “1”
    brief: test feature updated
    created_at: 2009-10-24 11:18:11
    attributes_cache: {}

Hi –

On Sat, 24 Oct 2009, nin_d wrote:

@features = @project.features.find(:all, :include => :owner)

and dump for @features in view is where i see only two features being
loaded and not the corresponding owner (only 1 in this case, with id

Look again in your original post. There’s a debug dump of a Feature
that has no owner_id.

David


The Ruby training with D. Black, G. Brown, J.McAnally
Compleat Jan 22-23, 2010, Tampa, FL
Rubyist http://www.thecompleatrubyist.com

David A. Black/Ruby Power and Light, LLC (http://www.rubypal.com)

On Oct 24, 3:14 pm, nin_d [email protected] wrote:

In server log, I do see query for fetching users with id=1. How this
is not appearing in the index view??

Is there a user with id 1? Get it working without :include, then worry
about the eager loading.

Fred

In server log, I do see query for fetching users with id=1. How this
is not appearing in the index view??

========= Server Log

Processing FeaturesController#index (for 127.0.0.1 at 2009-10-24
19:42:45) [GET]
Parameters: {“project_id”=>“1”}
[4;36;1mProject Columns (0.0ms) [0m [0;1mSHOW FIELDS FROM
projects [0m
[4;35;1mProject Load (0.0ms) [0m [0mSELECT * FROM projects
WHERE (projects.id = 1) [0m
[4;36;1mFeature Load (0.0ms) [0m [0;1mSELECT * FROM features
WHERE (features.project_id = 1) [0m
[4;35;1mFeature Columns (16.0ms) [0m [0mSHOW FIELDS FROM
features [0m
[4;36;1mUser Columns (16.0ms) [0m [0;1mSHOW FIELDS FROM users
[0m
[4;35;1mUser Load (0.0ms) [0m [0mSELECT * FROM users WHERE
(users.id = 1) [0m
Rendering template within layouts/features
Rendering features/index
[4;36;1mCACHE (0.0ms) [0m [0;1mSELECT * FROM projects WHERE
(projects.id = 1) [0m
[4;35;1mCACHE (0.0ms) [0m [0mSELECT * FROM projects WHERE
(projects.id = 1) [0m
Rendered common/_main_menu (16.0ms)
Rendered common/_project_menu (0.0ms)
Completed in 141ms (View: 47, DB: 32) | 200 OK [http://127.0.0.1/
projects/1/features]

Fred, thanks! there s no user with id 1. My bad!

While destroying a record, is there any easier way (a hook in
activerecord) to get warning/error that record belongs to other
records (if at all it does)?

On Oct 24, 4:26 pm, nin_d removed_email_ad[email protected] wrote:

Fred, thanks! there s no user with id 1. My bad!

While destroying a record, is there any easier way (a hook in
activerecord) to get warning/error that record belongs to other
records (if at all it does)?

You can set a dependent option on associations to control this sort of
stuff. If you want a real guarantee that this can’t ever happen, use a
foreign key constraint.

Fred

This forum is not affiliated to the Ruby language, Ruby on Rails framework, nor any Ruby applications discussed here.

| Privacy Policy | Terms of Service | Remote Ruby Jobs