Casting ActiveModel attribute on return - ruby-on-rails

In my Rails 3.1.1 project I have an ActiveModel that talks to API (ripped from Paul Dix's book, shortened for readability):
class Job
include ActiveModel::Validations
include ActiveModel::Serializers::JSON
ATTRIBUTES = [ :id,
:title,
:description,
:company_id ]
attr_accessor *ATTRIBUTES
validates_presence_of :title, :description
validates_numericality_of :company_id, :id
def initialize(attributes = {})
self.attributes = attributes
end
def attributes
ATTRIBUTES.inject(
ActiveSupport::HashWithIndifferentAccess.new
) do |result, key|
result[key] = read_attribute_for_validation(key)
result
end
end
def attributes=(attrs)
attrs.each_pair {|k, v| send("#{k}=", v)}
end
def read_attribute_for_validation(key)
send(key)
end
# More method definitions...
end
I instantiate #job in my controller, new action (company_id is a segnment key in the route: /companies/:company_id/jobs/new) like this:
#job = Job.new(company_id: params[:company_id])
Then, using CanCan, I check user's permissions to create to create a job. Basically, CanCan checks if current_user's company_id attribute matches job's company_id. This check fails because #job.company_id is returned as String.
Certainly, I can use params[:company_id].to_i while instantiating the object, but this seems like a workaround that I would have to repeat later.
Question: is there a way to make my Job ActiveModel more "type-aware" and make it return int for #job.company_id call?
I googled around, checked activemodel source code, but doesn't seem to find an answer. Any help is greatly appreciated.
Update
I was thinking more of something like schema block for ActiveModel, just like the one in ActiveResource.

attr_accessor *ATTRIBUTES
create a method like this:
def company_id
#company_id
end
You can just override that with
def company_id
#company_id.to_i
end

Answering my own question....
mosch's answer suggested to override the getter for company_id in my ActiveModel. However, I would have to repeat this for all of _id attributes in the model. Therefore, I decided to cast all of the '_id' attributes to integers while initializing the object. As follows:
def attributes=(attrs)
attrs.each_pair do |k, v|
if "#{k}".include? "_id"
send("#{k}=", v.to_i)
else
send("#{k}=", v)
end
end
end

I'm assuming your Company has_many => :jobs? If so, you could try
def new
#company = Company.find(params[:company_id])
#job = #company.jobs.new
end

Related

Implementing validations in PORO

I am trying to implement my own validations in Ruby for practice.
Here is a class Item that has 2 validations, which I need to implement in the BaseClass:
require_relative "base_class"
class Item < BaseClass
attr_accessor :price, :name
def initialize(attributes = {})
#price = attributes[:price]
#name = attributes[:name]
end
validates_presence_of :name
validates_numericality_of :price
end
My problem is: the validations validates_presence_of, and validates_numericality_of will be class methods. How can I access the instance object to validate the name, and price data within these class methods?
class BaseClass
attr_accessor :errors
def initialize
#errors = []
end
def valid?
#errors.empty?
end
class << self
def validates_presence_of(attribute)
begin
# HERE IS THE PROBLEM, self HERE IS THE CLASS NOT THE INSTANCE!
data = self.send(attribute)
if data.empty?
#errors << ["#{attribute} can't be blank"]
end
rescue
end
end
def validates_numericality_of(attribute)
begin
data = self.send(attribute)
if data.empty? || !data.integer?
#valid = false
#errors << ["#{attribute} must be number"]
end
rescue
end
end
end
end
Looking at ActiveModel, you can see that it doesn't do the actual validation when validate_presence_of is called. Reference: presence.rb.
It actually creates an instance of a Validator to a list of validators (which is a class variable _validators) via validates_with; this list of validators is then called during the record's instantiation via callbacks. Reference: with.rb and validations.rb.
I made a simplified version of the above, but it is similar to what ActiveModel does I believe. (Skipping callbacks and all that)
class PresenceValidator
attr_reader :attributes
def initialize(*attributes)
#attributes = attributes
end
def validate(record)
begin
#attributes.each do |attribute|
data = record.send(attribute)
if data.nil? || data.empty?
record.errors << ["#{attribute} can't be blank"]
end
end
rescue
end
end
end
class BaseClass
attr_accessor :errors
def initialize
#errors = []
end
end
EDIT: Like what SimpleLime pointed out, the list of validators will be shared across and if they are in the base class, it would cause all the items to share the attributes (which would obviously fail if the set of attributes are any different).
They can be extracted out into a separate module Validations and included but I've left them in in this answer.
require_relative "base_class"
class Item < BaseClass
attr_accessor :price, :name
##_validators = []
def initialize(attributes = {})
super()
#price = attributes[:price]
#name = attributes[:name]
end
def self.validates_presence_of(attribute)
##_validators << PresenceValidator.new(attribute)
end
validates_presence_of :name
def valid?
##_validators.each do |v|
v.validate(self)
end
#errors.empty?
end
end
p Item.new(name: 'asdf', price: 2).valid?
p Item.new(price: 2).valid?
References:
presence.rb
with.rb
validators.rb
class variable _validators
First, let's try to have validation baked into the model. We'll extract it once it's working.
Our starting point is Item without any kind of validation:
class Item
attr_accessor :name, :price
def initialize(name: nil, price: nil)
#name = name
#price = price
end
end
We'll add a single method Item#validate that'll return an array of strings representing errors messages. If a model is valid the array will be empty.
class Item
attr_accessor :name, :price
def initialize(name: nil, price: nil)
#name = name
#price = price
end
def validate
validators.flat_map do |validator|
validator.run(self)
end
end
private
def validators
[]
end
end
Validating a model means iterating over all associated validators, running them on the model and collecting results. Notice we provided a dummy implementation of Item#validators that returns an empty array.
A validator is an object that responds to #run and returns an array of errors (if any). Let's define NumberValidator that verifies whether a given attribute is an instance of Numeric. Each instance of this class is responsible for validating a single argument. We need to pass the attribute name to the validator's constructor to make it aware which attribute to validate:
class NumberValidator
def initialize(attribute)
#attribute = attribute
end
def run(model)
unless model.public_send(#attribute).is_a?(Numeric)
["#{#attribute} should be an instance of Numeric"]
end
end
end
If we return this validator from Item#validators and set price to "foo" it'll work as expected.
Let's extract validation-related methods to a module.
module Validation
def validate
validators.flat_map do |validator|
validator.run(self)
end
end
private
def validators
[NumberValidator.new(:price)]
end
end
class Item
include Validation
# ...
end
Validators should be defined on a per-model basis. In order to keep track of them, we'll define a class instance variable #validators on the model class. It'll simply by an array of validators specified for the given model. We need a bit of meta-programming to make this happen.
When we include any model into a class then included is called on the model and receives the class the model is included in as an argument. We can use this method to customize the class at inclusion time. We'll use #class_eval to do so:
module Validation
def self.included(klass)
klass.class_eval do
# Define a class instance variable on the model class.
#validators = [NumberValidator.new(:price)]
def self.validators
#validators
end
end
end
def validate
validators.flat_map do |validator|
validator.run(self)
end
end
def validators
# The validators are defined on the class so we need to delegate.
self.class.validators
end
end
We need a way to add validators to the model. Let's make Validation define add_validator on the model class:
module Validation
def self.included(klass)
klass.class_eval do
#validators = []
# ...
def self.add_validator(validator)
#validators << validator
end
end
end
# ...
end
Now, we can do the following:
class Item
include Validation
attr_accessor :name, :price
add_validator NumberValidator.new(:price)
def initialize(name: nil, price: nil)
#name = name
#price = price
end
end
This should be a good starting point. There're lots of further enhancements you can make:
More validators.
Configurable validators.
Conditional validators.
A DSL for validators (e.g. validate_presence_of).
Automatic validator discovery (e.g. if you define FooValidator you'll automatically be able to call validate_foo).
If your goal is to mimic ActiveRecord, the other answers have you covered. But if you really want to focus on a simple PORO, then you might reconsider the class methods:
class Item < BaseClass
attr_accessor :price, :name
def initialize(attributes = {})
#price = attributes[:price]
#name = attributes[:name]
end
# validators are defined in BaseClass and are expected to return
# an error message if the attribute is invalid
def valid?
errors = [
validates_presence_of(name),
validates_numericality_of(price)
]
errors.compact.none?
end
end
If you need access to the errors afterwards, you'll need to store them:
class Item < BaseClass
attr_reader :errors
# ...
def valid?
#errors = {
name: [validates_presence_of(name)].compact,
price: [validates_numericality_of(price)].compact
}
#errors.values.flatten.compact.any?
end
end
I don't understand the point to implement PORO validations in Ruby. I'd do that in Rails rather than in Ruby.
So let's assume you have a Rails project. In order to mimic the Active Record validations for your PORO, you need to have also 3 things:
Some kind of a save instance method within your PORO (to call the validation from).
A Rails controller handling CRUD on your PORO.
A Rails view with a scaffold flash messages area.
Provided all 3 these conditions I implemented the PORO validation (just for name for simplicity) this way:
require_relative "base_class"
class Item < BaseClass
attr_accessor :price, :name
include ActiveModel::Validations
class MyValidator
def initialize(attrs, record)
#attrs = attrs
#record = record
end
def validate!
if #attrs['name'].blank?
#record.errors[:name] << 'can\'t be blank.'
end
raise ActiveRecord::RecordInvalid.new(#record) unless #record.errors[:name].blank?
end
end
def initialize(attributes = {})
#price = attributes[:price]
#name = attributes[:name]
end
# your PORO save method
def update_attributes(attrs)
MyValidator.new(attrs, self).validate!
#...actual update code here
save
end
end
In your controller you have to manually process the exception (as your PORO is outside ActiveRecord):
class PorosController < ApplicationController
rescue_from ActiveRecord::RecordInvalid do |exception|
redirect_to :back, alert: exception.message
end
...
end
And in a view - just a common scaffold-generated code. Something like this (or similar):
<%= form_with(model: poro, local: true) do |form| %>
<% if poro.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(poro.errors.count, "error") %> prohibited this poro from being saved:</h2>
<ul>
<% poro.errors.full_messages.each do |message| %>
<li><%= message %></li>
<% end %>
</ul>
</div>
<% end %>
<div class="field">
<%= form.label :name %>
<%= form.text_field :name, id: :poro_name %>
</div>
<div class="actions">
<%= form.submit %>
</div>
<% end %>
That's it. Just keep it all simple.

Can't save record attributes to the database

class Contact < ActiveRecord::Base
attr_accessor :email
def initialize(data)
data.each { |k, v| send("#{k}=", v) }
end
end
In rails console
Contact.create!({"email"=>"foo#gmail.com"})
The record saved to the database has email as nil
Update:
The data is being passed in is JSON. I am getting all the data from the JSON and trying to save that into the database.
Did you try:
Contact.create!(email: "foo#gmail.com")
The email as a :symbol and no curly brackets?
Also, why are you initializing in your model?
With Mohamed El Mahallaway, I think your code setup could be improved (to negate initializing your model). I think you'll be better using the strong_params functionality of Rails:
#app/controllers/contacts_controller.rb
def new
#contact = Contact.new
end
def create
#contact = Contact.new(contact_params)
#contact.email = "foo#gmail.com"
#contact.save
end
private
def contact_params
params.require(:contact).permit(:email, :other, :params)
end
I may have miscalculated your competency with Rails, but this is the "Rails" way to save the correct data to your model :) You may to have a before_save method in your model to use the email attribute, considering it's a virtual attribute

Find_by_slug with Mongoid method undefined

I am using Mongoid(3.0.23) and I want to add nicer URL's, I have followed this rails cast but for some reason my site throws an undefined error for the find_by_slug method. I have read about some gems I could use but it seems pointless for such a simple task.
Model
validates :slug, :uniqueness => true
before_validation :generate_url
def generate_url
self.slug ||= self.title.parameterize if slug.blank?
end
def to_param
slug
end
field :slug
View
<% #events.each do |e| %>
<%= link_to e.title, event_path(e) %>
<% end %>
Controller
def show
#event = Event.find_by_slug!(params[:id])
end
Maybe try:
Event.find_by(slug: params[:id])
Also, not sure if it's necessary but you could specify the type:
field :slug, type: String
Mongoid defines the attribute finder, but not the bang version.
Event.find_by_slug(params[:id])
# => valid
Event.find_by_slug!(params[:id])
# => not defined
In any case, given the way ActiveModel is taking and according to best practices, it's better for you define all the public API of your model.
class Event
def self.find_by_slug!(slug)
where(slug: slug).first || raise(Mongoid::Errors::DocumentNotFound, self, slug: slug)
end
end
You can also re-use find_by_slug, but as I said, because ActiveRecord is deprecating find_by_attribute, I prefer to write the code directly.

Organic Rails Data-Model with NoSQL Database

I'd like to make full use of the organic character of a NoSQL document and build a dynamic data model which can grow, be changed, and is different for most datasets. Below is the model SomeRequest.rb with the code to set and get from Couchbase, but I can't get the function addOrUpdate(key, value) to work:
undefined method `each' for "0":String
Completed 500 Internal Server
Error in 16ms NoMethodError (undefined method `each' for "0":String):
config/initializers/quiet_assets.rb:7:in `call_with_quiet_assets'
Is the returning error. Is there a way to make this work, to add (or update existing) keys and save the document to the database afterwards?
class SomeRequest < Couchbase::Model
include ActiveModel::Validations
include ActiveModel::Conversion
extend ActiveModel::Callbacks
extend ActiveModel::Naming
# Couch Model
define_model_callbacks :save
attribute :session_id
attribute :views, :default => 0
attribute :created_at, :default => lambda { Time.zone.now }
# iterate through attr keys and set instance vars
def initialize(attr = {})
#errors = ActiveModel::Errors.new(self)
unless attr.nil?
attr.each do |name, value|
setter = "#{name}="
next unless respond_to?(setter)
send(setter, value)
end
end
end
def addOrUpdate(key, value)
self[key] = value
end
def save
return false unless valid?
run_callbacks :save do
Couch.client.set(self.session_id, self)
end
true
end
def self.find(key)
return nil unless key
begin
doc = Couch.client.get(key)
self.new(doc)
rescue Couchbase::Error::NotFound => e
nil
end
end
end
Why don't you like to use find, save and create methods from couchbase-model gem?
class Couchbase::Error::RecordInvalid < Couchbase::Error::Base
attr_reader :record
def initialize(record)
#record = record
errors = #record.errors.full_messages.join(", ")
super("Record Invalid: #{errors}")
end
end
class SomeRequest < Couchbase::Model
include ActiveModel::Validations
attribute :session_id
attribute :views, :default => 0
attribute :created_at, :default => lambda { Time.zone.now }
validates_presence_of :session_id
before_save do |doc|
if doc.valid?
doc
else
raise Couchbase::Error::RecordInvalid.new(doc)
end
end
def initialize(*args)
#errors = ActiveModel::Errors.new(self)
super
end
end
And you might be right, it worth to add validation hooks by default, I think I will do it in next release. The example above is valid for release 0.3.0
What considering updateOrAdd I recommend you just use method #save and it will check if the key is persisted (currently by checking id attribute) and if the record doesn't have key yet, it will generate key and update it.
Update
In version 0.4.0 I added validation hooks into the gem, so the example above could be rewritten simpler.
class SomeRequest < Couchbase::Model
attribute :session_id
attribute :views, :default => 0
attribute :created_at, :default => lambda { Time.zone.now }
validates_presence_of :session_id
end

Rails 3: alias_method_chain to set specific attribute first

When user's create a post I'd like to set the user_id attribute first. I'm trying to do this using alias_method_chain on the arrtibutes method. But I'm not sure if this is right as the problem I thought this would fix is still occurring. Is this correct?
Edit:
When my users create a post they assign 'artist(s)' to belong to each post, using a virtual attribute called 'artist_tokens'. I store the relationships in an artist model and a joined table of artist_ids and post_ids called artisanships.
I'd like to to also store the user_id of whomever created the artist that belongs to their post (and I want it inside the artist model itself), so I have a user_id column on the artist model.
The problem is when I create the artist for each post and try to insert the user_id of the post creator, the user_id keeps showing as NULL. Which is highly likely because the post's user_id attribute hasn't been set yet.
I figured to get around this I needed to set the user_id attribute of the post first, then let the rest of the attributes be set as they normally are. This is where I found alias_method_chain.
post.rb
attr_reader :artist_tokens
def artist_tokens=(ids)
ids.gsub!(/CREATE_(.+?)_END/) do
Artist.create!(:name => $1, :user_id => self.user_id).id
end
self.artist_ids = ids.split(",")
end
def attributes_with_user_id_first=(attributes = {})
if attributes.include?(:user_id)
self.user_id = attributes.delete(:user_id)
end
self.attributes_without_user_id_first = attributes
end
alias_method_chain :attributes=, :user_id_first
EDIT:
class ArtistsController < ApplicationController
def index
#artists = Artist.where("name like ?", "%#{params[:q]}%")
results = #artists.map(&:attributes)
results << {:name => "Add: #{params[:q]}", :id => "CREATE_#{params[:q]}_END"}
respond_to do |format|
format.html
format.json { render :json => results }
end
end
In your controller, why not just do this:
def create
#post = Post.new :user_id => params[:post][:user_id]
#post.update_attributes params[:post]
...
end
But it seems to me that it would be much better to create the artist records after you've done validation on the post rather than when you first assign the attribute.
EDIT
I would change this to a callback like this:
class Post < ActiveRecord::Base
attr_accessor :author_tokens
def artist_tokens=(tokens)
#artist_tokens = tokens.split(',')
end
after_save :create_artists
def create_artists
#artist_tokens.each do |token|
...
end
end
end

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