I am developing a small mass administration rails app for our church.
It shall allow the planning of future masses, essentially assigning different tasks to different ministrants (acolyte/server/altar boy?).
One should be able to select serving ministrants (through checkboxes) and assign a task to each ministrant (through option lists), per mass (it does not need to be the same every mass).
My questions are:
1. How would the migrations look like? I.e. which fields of what type are required?
2. How would the model associations look like? Currently, I am assuming 3 classes (Mass, Ministrant, Task).
I found this question: Correct Model Data Structure? (My 1st Rails App)
and it looks similar but I don't really know how to apply the solution on this example...
I'd appreciate your help!
3 models: mass, ministrant and task.
In your console:
rails g model Mass date:datetime
rails g model Ministrant name:string role:string
rails g model Task name:string ministrant_id:integer mass_id:integer
In your ruby files:
class Mass < ActiveRecord::Base
has_many :tasks
has_many :ministrants, :through => :tasks
end
class Ministrant < ActiveRecord::Base
has_many :tasks
has_many :masses, :through => :tasks
end
class Task < ActiveRecord::Base
belongs_to :ministrant
belongs_to :mass
end
Related
I have two classes in my Rails API database, that I have just created a joining table for. I had seeded both classes previously so they have data. Now I would like to seed the joining class with id's from the existing data.
This is what the models look like for the first two classes:
class Stakeholder < ApplicationRecord
has_many :project_stakeholders
has_many :projects, through: :project_stakeholders
end
class Project < ApplicationRecord
has_many :project_stakeholders
has_many :stakeholders, through: :project_stakeholders
end
This is the model for my joining class:
class ProjectStakeholder < ApplicationRecord
belongs_to :project
belongs_to :stakeholder
end
Now I have two questions:
How to populate the joint class with data from the two first classes (project_id and stakeholder_id).
How can I check in the Rails console for values in the ProjectStakeholder class?
I have researched and tried different options from Stackoverflow but they don't seem to work. Rails guides do not provide an answer either, from what I have seen. Would be very grateful for some ideas!
You can just assign stakeholders to the project after creation
Project.first.stakeholders << Stakeholder.limit(5)
Project.second.stakeholders << Stakeholder.limit(5).offset(5)
You can check it in console in different ways:
Project.first.stakeholders.pluck(:id)
ProjectStakeholder.first
I am having trouble wrapping my head around what I'd consider a more complex association and was hoping someone could help point me in the right direction.
I have four models:
user
profile
feed_group
feed
All 4 of these obviously have their own fields and data stored within. My goal is to have a summary database table called "user_detail" (I am open to calling it something different if Rails has its conventions), which has the following 4 fields:
user_id
profile_id
feed_group_id
feed_id
What would my model associations look like?
Thanks.
You can create the model through a migration like this:
rails g model UserDetail user:references profile:references feed_group:references feed:references
Within the created file models/user_detail.rb you will find the relations:
class UserDetail < ActiveRecord::Base
belongs_to :user
belongs_to :profile
belongs_to :feed_group
belongs_to :feed
end
Also, add references to UserDetail in all the referenced models, eg. in models/user.rb add has_many :user_details, etc.
As I read your question, that's all you need.
I am relatively new to ruby/rails and I have the following question:
I am working on a scheduling app and have a model named Classes and another named ClassEntries. The relationship between them is that each user can have multiple class entries per semester, each relating to one class. Each record in the Classes table belongs to a specific University. A User can have multiple entries in the ClassEntries table for 1 semester (typically 5). Their schedule is comprised of all their ClassEntries with the same semester ID.
I am not sure whether I should have a third model called Schedule that brings together the info in the ClassEntries and Classes models for the user at hand. I originally wrote this functionality in PHP and I simply used a MySQL JOIN to gather the necessary information. In Rails it seems that there should be a better way to accomplish this.
What would be the best way of going about this in Rails?
Many thanks
So, what you are looking for is pretty much associations in Rails.
You would have the following:
def User < ActiveRecord::Base
has_many :course_entries
has_many :courses, :through => :class_entries
end
def CourseEntry < ActiveRecord::Base
belongs_to :user
belongs_to :course
end
def Course < ActiveRecord::Base
has_many :course_entries
has_many :users, :through => :class_entries
end
With those associations set up, Rails would allow you to do such things like
some_user.courses or some_course.users and it will make the joins through CourseEntry for you.
Let me know if this helps. If you need me to go more in depth let me know.
Hopefully I don't get flamed for this one too bad - I've tried my very hardest to find an answer to no avail.
I was wondering if someone could help me figure out how to properly declare associations in Ruby on Rails (3). At the moment, I have 3 models:
#room.rb
class Room < ActiveRecord::Base
has_many :check_ins
end
#check_in.rb
class CheckIn < ActiveRecord::Base
belongs_to :user
belongs_to :room
end
#user.rb
class User < ActiveRecord::Base
has_one :check_in
end
So far, I haven't done any migrations to add foreign_key columns to any of my tables (does Rails do this for you?).
I'm confused about why the command CheckIn.first.user returns nil whereas the command User.first.check_in returns SQLite3::SQLException: no such column. The same happens with respect to CheckIn.first.room and Room.first.check_ins, respectively. What would I need to do in order to have User.first.check_in return the CheckIn object associated with the first user and Room.first.check_ins return the set of CheckIns associated with the first Room?
Any help would be GREATLY appreciated.
Charlie
How did you originally generate these models? Did you just make the model files, or did you use rails' model generator (which also generates a migration for you)?
#room.rb
class Room < ActiveRecord::Base
has_many :check_ins
end
#check_in.rb
class CheckIn < ActiveRecord::Base
belongs_to :user
belongs_to :room
end
#user.rb
class User < ActiveRecord::Base
has_one :check_in
has_one :room, :through => :check_in
end
In db/migrations/34612525162_something_something.rb You need to make sure you have migrations that set these tables up for you. The easiest way for you to do it would be to run this command in a console, modify the commands to use the fields you want, the *_id fields are required for your associations to work:
rails generate model user name:string email:string otherfield:integer
rails generate model check_in user_id:integer room_id:integer
rails generate model room number:integer
Note that these will also generate model files for you, since you already have these 3 model files it'll ask you if you want to overwrite them, or skip the files. You can skip them and it should be just fine. If you already had the migrations for part of the data in these models then you can just add the user_id and room_id fields to the check_in model by running this generator instead:
rails generate migration AddIdsToCheckIn user_id:integer room_id:integer
For rails 2.3.x replace rails generate with script/generate. Next you can inspect your migration(s) by opening the files up in db/migrate.rb and modify them there if you need to. Finally, run the migrations:
rake db:migrate
And it should work out for you. Note that I added a has_one, :through => relationship to User - this is so that you can do #user.room without having to make 3 chains: #user.check_in.room
You need to add the migrations yourself (or if you aren't live, you can modify an existing migration). Basically, you need to give the belongs_to side of the relationship a foreign key.
There is absolutely no reason to get flamed don't worry :) It seems here that you are trying to do a one to many association, but you're actually doing a many to many one.
If a user has one check in, it means that he/she has one room. So, you could just have :
user has_one room
room belongs to user
and room has a user_id.
Hope that helps :)
I have some problem trying to understand when building a rails app with several models and relation ships between them...
If I take a basic example like a model Group, a model User and a model Car
class Group < ActiveRecord::Base
has_many :users
end
class User < ActiveRecord::Base
belongs_to :group
has_many :cars
end
class Car < ActiveRecord::Base
belongs_to :user
end
Will those relation ship statements automatically create the following functions:
group.users
user.group
user.cars
car.user
It seems that we sometimes need to have to create "references" in migration (like adding a reference toward User in Car table) but is this always required ?
In this case, what is the difference of creating the migration and of adding the relationship statement in the models ? I sometimes have the feeling this is used for the same purpose.
Thanks a lot for your help,
Regards,
Luc
The association declarations are there for Rails only. You have to define the foreign keys (references) in the database, so that Rails can properly save the data.
Remember, despite all the magic, it's still backed by a relational database, so good practices there will pay off in the long run.