Here's my use case:
I've got a collection full of sales tax rates that have been imported from CSV files. I created the Mongoid model to mirror the field names (these are not changeable):
class SalesTaxRate
include Mongoid::Document
field :state, type: String
field :zip_code, type: String
field :tax_region_name, type: String
field :tax_region_code, type: String
field :combined_rate, type: Float
end
Next, I'm building a model for use in my app. Let's say I want to create something called a Location:
class Location
include Mongoid::Document
field :name, type: String
field :street, type: String
field :city, type: String
field :state, type: String
field :zip_code, type: String
end
I'd like to be able to get a location's sales tax rate simply by calling something like this:
home = new Location(...)
home.sales_tax_rate
I'll never be setting the rate via home, just looking it up.
What's the "right" way to do this? I can think of two approaches -- the simple way seems to be just to define a method that does the lookup, as so:
class Location
...
def sales_tax_rate
SalesTaxRate.where(zip_code: self.zip_code).first.combined_rate
end
And this works. But I'm wondering whether I should be using a belongs_to association and, if so, why and how best to do that.
Still learning the ropes here, so apologies if this is a novice/silly question. Many thanks in advance!
If you have an index on zip_code in model SalesTaxRate what you are doing is essentially the same as what belongs_to will do. Just have a nil check in your code to ensure that it doesn't fail:
SalesTaxRate.where(zip_code: self.zip_code).first.try(:combined_rate)
# or
rate = SalesTaxRate.where(zip_code: self.zip_code).first
rate.nil? ? nil : rate.combined_rate
If you still want to go belongs_to route, you can define zip_code to be the identity in your SalesTaxRate. But you should take care of few things if you do that: First, all the zip codes in imported data need to be unique. Second, your location model can not have any zip code which is not available in SalesTaxRate otherwise you will face issues.
Related
I currently have the columns id, name, email, linkedin, company, contacted, recruiter, student and I want to add a new one called responded. I'm only finding answers on how to add new columns to all the existing instances in my db. So I did try this:
db.people.update({}, {$set: {"responded": false}}, false, true)
All my existing instances have a field :responded set to false by default. When I try to add a new person now I'm getting this error:
Mongoid::Errors::UnknownAttribute in PeopleController#create
message: Attempted to set a value for 'responded' which is not allowed on the model Person. summary: Without including Mongoid::Attributes::Dynamic in your model and the attribute does not already exist in the attributes hash, attempting to call Person#responded= for it is not allowed. This is also triggered by passing the attribute to any method that accepts an attributes hash, and is raised instead of getting a NoMethodError. resolution: You can include Mongoid::Attributes::Dynamic if you expect to be writing values for undefined fields often.
MongoDB does not have "columns", it does not have tables either. You have documents with fields.
I imagine you are using MongoID for your models, so you only need to define the field on your model
class Person
include Mongoid::Document
field :first_name, type: String
field :middle_name, type: String
field :last_name, type: String
field :responded, type: Boolean # something like this
end
https://docs.mongodb.com/mongoid/current/tutorials/mongoid-documents/#fields
I have a requirement to convert an ActiveRecord model class into a MongoDB Document class automatically. I am able to do so using a rails generator which will read the attributes of a model and generate the new document.rb.
If a ActiveRecord model class looks like below:
class Project < ActiveRecord::Base
attr_accessible :completed, :end_date, :name, :start_date
end
Then, a generated class confirming to Mongoid's structure will be as below:
class ProjectDocument
field :name, type: String
field :start_date, type: Date
field :end_date, type: Date
field :completed, type: Boolean
field :created_at, type: Time
field :updated_at, type: Time
end
But I don't want to store a different document files, one for each model. I want to be able to generate this document class on the fly, whenever the rails application is started.
Is this possible? Is this approach of generating and using classes from memory advised? I don't have constraints on changes to AR model structure; the document is flexible w.r.t data structure and changed columns will get added automatically.
My first attempt would look something like this:
klass = Project
new_class = Object.const_set(klass.name + "Document", Class.new)
klass.columns.each do |c|
new_class.class_eval do
field c.name.to_sym, type: c.type
end
end
You'll almost certainly have to do something more complicated to set the field type correctly, but this should give you a good starting point.
I started to use the mongoid gem in my project, and I'm a little confused about how it store and get the information on the database. I have fields of specifics types in my models, but when I get it from the DB it returns a Hash.
Here is my models:
service.rb
class Service
include Mongoid::Document
field :username, type: String
field :strategy, type: Strategy
field :design, type: Design
end
strategy.rb
class Strategy
include Mongoid::Document
field :name, type: String
field :description, type: String
field :resources, type: Resources
field :scalability, type: Scalability
field :localization, type: Localization
field :contact, type: Contact
end
If I initialize a new service #service, and do #service.class it returns Service, the right one, but if I try do #service.strategy.class, it returns Hash, and not Strategy, like I was expecting. I read on the mongoid manual there are the "Custom field serialization", what I think allows me to do what I want. But I was wondering if there are not any other way to do that easily, because I have lots of models to change.
I have the following (using mongoid):
class FacebookUser
include Mongoid::Document
include Mongoid::Timestamps
field :uid, type: String
field :friends, type: Array
end
I am using mongoid and am wondering whether to store facebook_ids and facebook_ids_of_friends(Array) as BigDecimal, Integer or String. I will be using the uid for queries so am somewhat concerned about speed.
OR:
class FacebookUser
include Mongoid::Document
include Mongoid::Timestamps
field :uid, type: Integer
field :friends, type: Array #???How do I get this to store ints instead of strings
end
To avoid casting things repeatedly, I believe that the first option is better but wanted to get another opinion? In addition, how would I store an Array with Integer if I go with option 2?
Use a string. The only reason to use numeric types is if you will be doing calculations on the data. It is nonsensical to try to add two user id's so they should not be stored as integers.
Try this
class FacebookUser
identity :type => String
end
due to line identity :type => String your id of model will become String type and you can save facebook user id(uid) directly in there instead of creating a new field. The queries like finding users will be really easy and fast
For e.g.
find one user
FacebookUser.find(facebook user id)
This is my 2nd day playing with Ruby on Rails, so please be gentle :)
I have a very (hopefully) simple question: I want to set a publish date on my model, when it is indeed being created. I am using Mongoid, and it looks like this:
class Page
include Mongoid::Document
field :content, type: String
field :title, type: String
field :published_on, type: DateTime
end
Here is the question: should I set the published_on field from the create action, just before the call to #page.save? Or is there a better, more idiomatic way?
If I do it like that, meaning, calling #page.published_on = Date.now from within the controller's action, I get a warning:
Cannot find 'published_on=' for type 'Page'
If you put
class Page
include Mongoid::Document
include Mongoid::Timestamps
you get the rails automagic fields created_at and updated_at