I've had some issues with this before when creating applications and I think I'm starting to run into it again, hence I'm asking this on StackOverflow to save me a lot of time.
I've spent the last few weeks setting up a perfected product model for my system. The model performs exactly as I want it to and has several complex features (such as search via sunspot). I wanted to setup the category to product structure before I started this heavy development - however struggling with this kind of thing was just putting me off creating the application so I got straight into the product structure.
Now I've got the product model setup - what would be the easiest way to add a category ownership to encompass the products? (All products have a category_id column which store their father category id)
My plan is to have the category index to be a list of all the categories, the category show to be a list of the products inside that category and the product show being the view of the actual product. This would eliminate the product index and so I'll have to come up with a way to port the search feature (sunspot) from my index view to the category show somehow.
As for the actual listing of the products - I assume I'll have to do some kind of partial? (I don't know a lot about it).
Most basically, my relationships are planned to be:
category:
has_many :products
product:
has_one :category
My products then have a category_id column to store the ID of it's parent category.
Any tips on how to accomplish the relationships (category show to list the products etc)?
Best Regards,
Joe
Relationships like the one you're wanting are built into ActiveRecord support. Understanding the model relationships in Rails is critical to doing anything in Rails that's non-trivial, so study up.
Also, the relationship you're looking for is something like:
product:
belongs_to :category
category:
has_many :products
Related
I'm building a site that tracks donations and sales of items in a school auction.
Items can be sold individually or in lots, which are just groups of items bundled for sale as a single unit (like a gift certificate for a dinner Item bundled with a gift certificate for movie tickets Item).
Both of these things (Items and Lots) share fields like name, description, value. But Items have additional fields, like the donor, restrictions of use, type of item, etc.
I started by creating a table called Lot and an association table that lets Lots contain 1+ Items.
That works great for Lots. But that leaves me with a problem:
When Buyers win I need to record the win and the price. I'm doing that with a Win table that associates the Buyer with the Lot and the winning price.
But how do I deal with all the Items that aren't assigned to Lots? Should every item be in a Lot, just singly? That would make sense because it would work with the Win table scheme above, but I would need to automatically create a Lot for every Item that isn't already in another Lot. Which seems weird.
I'm sure this is a simple problem, but I can't figure it out!
Thanks!
Your approach of treating every item as a lot should be the winning one. It may sound weird, but it will make things way easier in the long run.
I have to deal on a daily base with a database where a similar problem was 'solved' the other way round, meaning keeping bundles of items and items apart and that proved to be a great pita (and for sure I'm not talking about a flat round bread here).
This database is both backbone for statistical evaluations and a bunch of (web) applications and on countless occasions I run into trouble when deciding which table to chose or how to level the differences between those two groups in querying and in coding.
So, even if your project will be rather small eventually, that is a good idea.
Yes, you need to provide a method to put every item in a lot, but this trouble is to be taken just once. On the other hand your queries wouldn't become significantly more complex because of that 'extra' table, so I'd definitely would chose this way.
It sounds like you have an Auction model that could have one or many Items. Then you could have two different types of Auctions, Auction::Single and Auction::Lot. Price would be a column on Auction. Auction has many Bids which is a join model between the Auction and the User (or Bidder). That join model would also store the bid price. When the Auction is over, you could create a separate Win record if you want, or just find the Winner through the highest Bid from Auction.
It would be helpful if you showed some code. But, what you want is a polymorphic association. So, something like:
class Item
has_one :win, as: :winnable
belongs_to :lot
end
class Lot
has_one :win, as: :winnable
has_many :items
end
class Win
belongs_to :buyer
belongs_to :winnable, polymorphic: true
end
Fairly new to rails and trying to understand which relationships to use before going forward.
I have two models: orders and items. This is a many to many relationship, but I'm unsure of which relationship to use.
Orders might have delivery time, quantity of items, etc.
Lastly, what would you call the model joining orders and items if using HMT?
If you need to know anything else about the relationship of the item on a particular order, you need HMT.
If your items change price in the future, do you want to know how much they were sold for on orders in the past?
In this type of requirement, I've always had many "LineItem" records for an order, and the line_item instances belong_to to the item and order, and record the pricing and/or quantity for that order.
HMT vs HABTM? There are so few times that all you need is a many-to-many, that I'd almost always go with HMT for the extra ability to add more information to the association.
This seems like a classic case of HABTM, and the example given in the Rails Guides is perfect. The choice comes down to whether you need any other data or logic on the join model itself. If so, then use the HMT, where you will create a third active_record model to serve as the join table. You can name that anything you want. But it seems like HABTM will work for you, and all you need to setup is the join table with the default name (items_orders) in your migration, and rails will take care of everything else for you.
class Order < ActiveRecord::Base
has_and_belongs_to_many :items
end
class Item < ActiveRecord::Base
has_and_belongs_to_many :orders
end
I am making an app in which there are three models individual, company and event.
company,event and individual lies in a single category.
here the company can create an event where they can choose multiple interests from categories and search for individuals that lies in that categories also when individual signs up they can choose multiple interests from categories table to find the companies of the interests and this same applies for company.
the solution I want is to prepare the best logic for this
my assumption is to create an Interest model where company , event and individuals has_many interests and interest belongs_to category
but this assumption seems to be confusing
Please suggest some logics
Let me try and condense my question:
I want to display data from multiple tables in a particular view. I want to list every person I have in a "People" table, and append there job on an "Affiliations" table listed with their company from an "Employers" table. Affiliations should belongs_to People and Employers, and Employers and People have_many Affiliations. What would the migration and controller look like?
I'm not entirely sure if this is the same as what you're asking, but using has_many and belongs_to may be a better solution. Using these associations would allow an employee to have many employers and then simply get the most recent one.
Please feel free to correct me if this isn't what you are asking.
For practice I'm writing a shopping website where we have tables User and Item. A user obviously has_many items (when they are added to their basket), but the item, it belongs_to a User, even though many users will have the same item in their basket?
Furthermore, what if I want a list of items a user has added to their basket, but also a list of items they have viewed (for making suggestions based on searches), would it be better to have some 'through' tables: Basket and Viewed?
When you have this many-to-many relationships, you can use the HABTM schema:
Class User...
has_and_belongs_to_many :items
However, most of the time webshops use orderlines to keep up with items that users are purchasing. This means that an 'user' 'has_many' 'orderlines', an 'item' 'has_many' 'orderlines', an 'orderline' 'belongs_to' an 'user' and to an 'item'.
And maybe your orderlines will just be copies of items, and won't have a direct link because you don't want to alter the orderline after they have been processed. It really depends on the focus of your shop which scheme suits your needs.
Try to find some examples on the web and think about how you want to handle items, orders and baskets.
I'm used to separate things that are not the same, even if the relationship is one-to-one. So first of all I would recommend users from baskets (1:1-relationship).
After that a basket contains many items and items can be in multiple baskets (m:n-relationship). Make sure, that maybe a user likes to buy the same item multiple times.
views can be realised as a linking table between users and items: users have many views and items have many views, but one view is always linked to exactly one user and one item.