How do I create custom "association methods" in Rails 3? - ruby-on-rails

I've read this article, but it's for Rails 1.x.
I'd really like to create my own association methods:
user = User.find(1)
# Example of a normal association method
user.replies.create(:body => 'very informative. plz check out my site.')
# My association method
user.replies.find_by_spamminess(:likelihood => :very)
In Rails 3, what's the proper way of doing this?


The Rails 3 way of doing things is often to not use find methods, but rather scopes, which delays the actual database call until you start iterating over the collection.
Guessing at your first example, I would do:
in class Reply ...
scope :spaminess, lambda {|s| where(:likelyhood => s) }
and then using it:
spammy_messages = user.replies.spaminess(:very)
or to use it in a view
spammy_messages.each do |reply|
....
end


I think I found it!
If you search for "association extensions" the Rails API page for ActiveRecord::Assications, you'll see that this is the syntax (copied from that link):
class Account < ActiveRecord::Base
has_many :people do
def find_or_create_by_name(name)
first_name, last_name = name.split(" ", 2)
find_or_create_by_first_name_and_last_name(first_name, last_name)
end
end
end

Related

Rest Api Ruby On Rails Nested Models

I'm kinda new to the whole rails/ruby thing. I've built a restful API for an invoicing app. Summary of models is below.
class Invoice < ActiveRecord::Base
has_many :pages
end
class Page < ActiveRecord::Base
belogs_to :invoice
has_many :rows
end
class Row < ActiveRecord::Base
belogs_to :page
end
I would like to be able to include related models in one rest call. I can currently do one level of nesting. For example i can get an Invoice with all its pages /invoices?with=pages is the call i would make. In controller i would create a hash array from this as per below(probably not the best code you've seen):
def with_params_hash
if(params[:with])
withs = params[:with].split(',')
withs.map! do |with|
with.parameterize.underscore.to_sym
end
withs
else
nil
end
end
This will return a hash as array e.g [:pages]
In the controller i use it as
#response = #invoice.to_json(:include => with_params_hash)
This works fine. I would like to be able to include nested models of say page.
As you know this can be done this way:
#invoice.to_json(:include => [:page => {:rows}])
The first question i guess is how do i represent this in the URL? I was thinking: /invoices?with=pages>rows. Assuming thats how I decide to do it. How do i then convert with=pages>rows into [:pages => {:rows}]

Why don't you use jbuilder? Will be easiest and you will can nest all models you want.
https://github.com/rails/jbuilder

So i ended up going with the format below for url:
/invoices?with=pages>rows
The function below will generate the function required:
def with_params_hash
final_arr = []
with_array = params[:with].split(',')
with_array.each do |withstring|
if withstring.include? ">"
parent = withstring[0..(withstring.index('>')-1)].parameterize.underscore.to_sym
sub = withstring[(withstring.index('>')+1)..withstring.length].parameterize.underscore.to_sym
final_arr << {parent => {:include => sub}}
else
final_arr << withstring.parameterize.underscore.to_sym
end
end
final_arr
end
Usage in the controller looks like:
#invoice.all.to_json(:include => with_params)
Alternatively as per #DavidGuerra's idea https://github.com/rails/jbuilder is not a bad option.

Rails 3.1 attr_accessible verification receives an array of roles

I would like to use rails new dynamic attr_accessible feature. However each of my user has many roles (i am using declarative authorization). So i have the following in my model:
class Student < ActiveRecord::Base
attr_accessible :first_name, :as=> :admin
end
and i pass this in my controller:
#student.update_attributes(params[:student], :as => user_roles)
user_roles is an array of symbols:
user_roles = [:admin, :employee]
I would like my model to check if one of the symbols in the array matches with the declared attr_accessible. Therefore I avoid any duplication.
For example, given that user_roles =[:admin, :employee]. This works:
#student.update_attributes(params[:student], :as => user_roles.first)
but it is useless if I can only verify one role or symbol because all my users have many roles.
Any help would be greatly appreciated
***************UPDATE************************
You can download an example app here:
https://github.com/jalagrange/roles_test_app
There are 2 examples in this app: Students in which y cannot update any attributes, despite the fact that 'user_roles = [:admin, :student]'; And People in which I can change only the first name because i am using "user_roles.first" in the controller update action. Hope this helps. Im sure somebody else must have this issue.

You can monkey-patch ActiveModel's mass assignment module as follows:
# in config/initializers/mass_assignment_security.rb
module ActiveModel::MassAssignmentSecurity::ClassMethods
def accessible_attributes(roles = :default)
whitelist = ActiveModel::MassAssignmentSecurity::WhiteList.new
Array.wrap(roles).inject(whitelist) do |allowed_attrs, role|
allowed_attrs + accessible_attributes_configs[role].to_a
end
end
end
That way, you can pass an array as the :as option to update_attributes
Note that this probably breaks if accessible_attrs_configs contains a BlackList (from using attr_protected)

how to index associated models using thinkingtank and indextank

We are using thinkingtank gem and having trouble indexing model associations, even simple ones. For example, a profile belongs to an institution, which has a name – we would like to do something like:
class Profile < ActiveRecord::Base
#model associations
define_index do
indexes institution(:name), :as => :institution_name
end
end
but that doesn't work. This must be very simple – what am I doing wrong?

a possible solution to this issue would be adding a method returning the element to index. For the profile.institution.name case:
# profile.rb
# ...
belongs_to :institution
# ...
define_index do
indexes institution_name
end
def institution_name
self.institution.name
end
# ...
Also the ", :as => ..." syntax is not supported on thinkingtank.
I would also recommend giving a try to Tanker: https://github.com/kidpollo/tanker
Regards.
Adrian

as_json not calling as_json on associations

I have a model with data that should never be included when it is rendered as json. So I implemented the class' as_json method to behave appropriately. The problem is when other models with associations with this model render json, my custom as_json is not being called.
class Owner < ActiveRecord::Base
has_one :dog
def as_json(options={})
puts "Owner::as_json"
super(options)
end
end
class Dog < ActiveRecord::Base
belongs_to :owner
def as_json(options={})
puts "Dog::as_json"
options[:except] = :secret
super(options)
end
end
Loading development environment (Rails 3.0.3)
ruby-1.9.2-p136 :001 > d = Dog.first
=> #<Dog id: 1, owner_id: 1, name: "Scooby", secret: "I enjoy crapping everwhere">
ruby-1.9.2-p136 :002 > d.as_json
Dog::as_json
=> {"dog"=>{"id"=>1, "name"=>"Scooby", "owner_id"=>1}}
ruby-1.9.2-p136 :004 > d.owner.as_json(:include => :dog)
Owner::as_json
=> {"owner"=>{"id"=>1, "name"=>"Shaggy", :dog=>{"id"=>1, "name"=>"Scooby", "owner_id"=>1, "secret"=>"I enjoy crapping everwhere"}}}
Thanks for the help

This is a known bug in Rails. (The issue is marked closed due to the migration to Github issues from the previous bug tracker, but it's still a problem as of Rails 3.1.)

As acknowledged above, this is an issue with the Rails base. The rails patch here is not yet applied and seems at least slightly controversial, so I'm hesitant to apply it locally. Even if applied as a monkey patch it could potentially complicate future rails upgrades.
I'm still considering RABL suggested above, it looks useful. For the moment, I'd rather not add another view templating language into my app. My current needs are very small.
So here's a workaround which doesn't require a patch and work for most simple cases. This works where the association's as_json method you'd like to have called looks like
def as_json(options={})
super( <... custom options ...> )
end
In my case I've got Schedule model which has many Events
class Event < ActiveRecord::Base
# define json options as constant, or you could return them from a method
EVENT_JSON_OPTS = { :include => { :locations => { :only => [:id], :methods => [:name] } } }
def as_json(options={})
super(EVENT_JSON_OPTS)
end
end
class Schedule < ActiveRecord::Base
has_many :events
def as_json(options={})
super(:include => { :events => { Event::EVENT_JSON_OPTS } })
end
end
If you followed the guideline that anytime you :include an association in your as_json() methods, you define any options you need as a constant in the model to be referenced, this would work for arbitrary levels of associations. NOTE I only needed the first level of association customized in the above example.

I've found that serializable_hash works just as you'd expect as_json to work, and is always called:
def serializable_hash(options = {})
result = super(options)
result[:url] = "http://.."
result
end

I ran into the same issue. I wanted this to work:
render :json => #favorites.as_json(:include => :location)
But it didn't so I ended up adding an index.json.erb with the following:
<% favs = #favorites.as_json.each do |fav| %>
<% fav["location"] = Location.find(fav["location_id"]).as_json %>
<% end %>
<%= favs.to_json.html_safe %>
Not a fix - just a work around. I imagine you did the same thing.

Update #John pointed out this is a known bug in Rails. A patch to fix it appears to be: at https://github.com/rails/rails/pull/2200. Nevertheless, you might try RABL, because its sweet.
I've always been frustrated with passing a complex set of options to create the JSON views I want. Your problem, which I experienced with Mongoid in Rails 3.0.9, prompted me to write JSON templates. But actually, if you're dealing with relations or custom api properties, it turns out that templates are way nicer.
Besides, dealing with different outputs seems like the View layer to me, so I settled on using RABL, the API templating language. It makes it super easy to build valid JSON and include any associations or fields.
Not a solution to the problem, but a better solution for the use case.

This was reported as a bug: http://ternarylabs.com/2010/09/07/migrating-to-rails-3-0-gotchas-as_json-bug/

Automatically mapping associations in Mongoid using params

I'm using Mongoid and when I .update_attributes on a model that has a references_one using params[:model_name] I get the error...
#model.update_attributes(params[:model_name])
undefined method `associations' for "...":String
I understand why this is happening. Mongoid is trying to map that .association_name to the string value in the params hash when what it wants is a reference to another Mongoid::Document. That I get.
What I'd like to know is if there is a global way to fix this. For the moment I've gotten around this issue by doing something like the following...
model_params = params[:model_name]
if model_params.has_key? :relationship
model_params[:relationship] = RelatedModel.first(:conditions => { :_id => model_params[:relationship] })
end
This works but I'd rather have a fix that fixes it every time so that I'm not manually mapping the related model every time I do an update. That would defiantly be a violation of DRY.

Here's sample module that you could include in all your models
module MyAppBase
def my_update_attributes(model_params,related_model)
if model_params.has_key? :relationship
model_params[:relationship] = related_model.first(:conditions => { :_id => model_params[:relationship] })
end
self.update_attributes(model_params)
end
end
#include it in your model classes
class MyModel < ActiveRecord::Base
include MyAppBase
#normal model code
end

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