I am trying to create network graph-like models, where I have Person, Organisation, Funder, Research Project etc... And I have connecting models of Relationships and Relation.
I'm fine with the notion of making my own interface to work with these objects, and ensuring objects are saved before they are added to relations, but for the life of me I can't get the Admin interface to work.
What happens is the Relation inlines just show up as blank OR I get the error the object doesn't exist after I have added them to form, when I save it all blows up.
I have created a full example and populated a few People, Organisations, etc in a SQLite db so that you can see it action... I've been struggling with this for years and despite poring over the docs for days and days, I can never quite get it to work. I'm hoping I have just got one concept wrong but as I said, this is driving me nuts, and what I generally do is, give up and make a model that is less "pure".
https://github.com/everythingability/manytomanywoes
p.s As an aside, it would be nice to have working examples to look at for some features with Django, wouldn't it?
Related
I am from UI/ColdFusion background, sorry if I am asking a silly question.
Let's say we have two models Book & Page and a book has many pages.
Normally i see rails devs do the below,
book = Book.find(id)
pages = book.pages
Which indeed executes two queries, one for getting the book and one for getting the pages.
Where as the same we can write like this,
Add a class method to Page model.
pages = Page.where(book_id: id)
This will execute one query but will still return the result.
But then why developers prefers the first approach instead of the second.
It's just the practice people follow
Usually, this scenario comes when you are accessing nested resources
book = Book.find(id)
pages = Page.where(book_id: id)
so to make sure you have the book available not just the orphan pages
pages = Page.where(book_id: id)
Whereas, with the above query you will get the pages even if the book is deleted, in case you don't have the dependent: :destroy for pages
From my practice, there are 2 answers to your question and the right answer would depend on the developer's experience.
Novice - Because that's how it was in the tutorials. The first Rails team I joined had a lead developer with no DB or SQL experience. He would not care or knew about the load on db server our code generated. This was quite common in early days of Rails (in my experience). ActiveRecords makes it so easy to forget that you have a DB in the background and it is easy to forget. Coming from java and php world myself, I would be asking why would we just write an SQL to join and do the heavy lifting on the server side.
Experienced - Experienced developers do it for the code readability. Because maintaining a readable code is cheaper in the long run. If your monitoring tools show that your DB server started to stress out, you can always profile and fix it (vertical scaling, adding caches on different levels of your architecture, etc). Also, when used in the controller, .find will generate 404 page if it can't find the record in the DB. Also, if you run your "custom" sql, you will lose "automatic" model-data relation maintained by AR for you. So, many choose to just do it that way.
So there you go. Unless you are working on very heavy load application, it is better to write a readable way.
Possibly a fairly basic question, but bear with me.
I'm building a page which has a number of pieces of modular content, represented by a ContentBlock model. Each ContentBlock has at least one link, each of which has a couple of different attributes. My initial approach was to just add these links as an array to the model, as there didn't seem to be any real need to store them separately in the database, and they don't have any logic of their own. Now that I'm looking at building a form for creating/editing a ContentBlock though, it seems like it would be much easier to build if there was a separate, nested model for the links.
I'm strongly considering converting to using a model, but my gut feeling is that it's kind of "wrong" to store something like as relatively trivial as the links are in the DB. Given I am still getting used to working with Rails, is this feeling misplaced? Should I just create models for anything and everything? Or should I be looking for some sort of minimum criteria before I do?
It is definitely easier to create forms for nested models. Since your links have attributes, I'd suggest making a model. I tend to err on the side of making models for concepts that can't easily fit into fields. If you're worried about query performance, you can always do eager loading.
I think depends on how much data you plan on managing, what you want to do against that data, what that data represents, etc...
One project we had was to build something that allowed creation of recipes for a group of restaurants. Recipe (some text, like instructions, etc...) -> Ingredient, we went with an array, as these were all single lined text and there would never be more than several hand fulls. Also, the ingredients had no further dependencies. The Recipes would only be rendered out to html and there would be no searching against them (not against the db at least).
Another project required building a Page, very similar to yours, but each "component" of the page did different things and some where linked to other objects in the app, like Videos and other assets, templates, etc... We had seen people do this type of stuff entire through a wysiwyg or through some JS way and saved the entire payload/structure in the DB. We found both to be extremely messy.
And one concern that came up was what happened if an asset/associated object was mistakenly or purposely deleted but lived throughout many pages. Using models allowed to ensure that if something got removed, it got removed within all it's linked associations (though this posed problems of it's own, but more regarding the page making sense when displayed more than anything else).
Also, our Page had the potential of becoming extremely large with different types of components with different looks and inter-activities, that this really was the only way we could properly manage it.
So I would look at your requirements and plan accordingly, context matters. And if you have to change it (which happens, a lot) then you'll change it.
Guys I am becoming completely nut on this...and can't figure out at all how come out of all this troubles.
I really need an holy help, or at least some suggestions about tutorial and guides about this problematic.
I believe that this is a very common task in many app, but I can't find nothing that help in this sense, not on stackoverflow, not on google, not on other rails forums that I know...I start to feel like a dumb!!!
Problem
(1) Models (the models that are involved)
User.rb
Item.rb (is nested in user: e.g. user/3/item/5)
(2) What I'd like to do
The current_user (the user that is logged in) can create an Item, and in the same form can decide to share it or no with many other users.
In this way, the item will be visible and accessible also for this users that we shared it with.
I understand that what is going to be involved here is:
(a) has_many :through relationship between item and user
(b) a joint table that we can call sharing (with item_id and user_id)
(c) eventually using different name for the user and use a :class_name to point to user
This is not hard to implement (and there are plenty of examples around).
What is really a mess, instead, is how build the controller (item controller), in order to perform in one shot, the creation of a new item, and the sharing operation (this means setting up the parameter in the joint table, and eventually create as many records as many users we are sharing with - array?)
And the other problem, that obviously is related with the controller, will be the view...how put all this in a single form, and allow the current_user to just click the button, and perform the item creation + the sharing operation?
Last thing, but not the least, how I need to deal with the fact that User is the same model of current_user??
I really don't know what I need to read or look up in order to let this work, I would love to see some example code,but at the same time I'd love to really understand the logic in all this, in order to be able to replicate it in other scenarios.
Please someone help me...I can't really move on in my app development without doing this, and this is also a crucial part of all the project.
Thanks so much for every small bit of help that I will receive.
Ok I have solved all my problems...that was not an hard task at the end (it's always easy saying that when you solved the issue:))
The only doubt that I still have is with the rails name convention:
Can be possible that using a name like sharing, for the joint model, that the final -ing is not very well handled by rails?
After many tentativeness performed to try to fix my problem, I discovered that everything was set up properly, and that just changing the joint table name from sharing to share, let the magic works!!!
I'm new to rails, so be nice.
I'm building a "rolodex" type application, and this question is about the best way to handle creating an entity along with several relationship entities at the same time.
For (a contrived) example:
My application will have a Person model, which has_one Contact_Info model. On the create.html.erb page for Person it makes sense for the user of my appliction to create the person, and the contact_info at the same time.
It doesn't seem right to include details for creating a contact directly in the create view/controller for person. What's the rails way to handle this?
Using nested attributes is the most common way to do this.
The actual documentation is here.
You want to use "Nested Forms". There is a great example of them in this blog post.
I'm also noob, but I had a similar issue with an app. I was using a tutor at the time and he basically said it was a good example of rails being opinionated. It sounds like you want to take the create action for two different models at the same time, which may be possible but probably very hard. Id suggest considering whether your data model could be modified, or find a way to make an acceptable user flow while collecting the data in different forms.
Update: while writing this the technical answer came in. Keep in mind, its perfectly okay to take the easy route if doing so helps you get the app out the door, and especially while you're still new.
I have been tasked with developing a new retail e-commerce storefront for my current job, and I am considering tackling it with RoR to A) Build a "real" project with my limited Rails knowledge, and B) Give management quick turnaround and feedback (they are wanting to get this done ASAP and their deadlines are rather unrealistic - I'm talking a couple of weeks to go from nothing to working model so they can start to market it with SEO/SEM and, I kid you not, "video blogging" because my boss heard that's the future).
We do have a database structure in place but it's absolutely terrible and was thrown together without rhyme nor reason, so I'm going to largely ignore it and create a new database from scratch; however, I have existing data that I need to load into the application (like I said, it's an e-commerce app and we have the product data). I need to massage this data into a usable format because our supplier provides it to us with cryptic, abbreviated column names and it's highly denormalized, especially in the categories (I've posted a question regarding it before - basically the categories table has six fields, one for each category/subcategory, with some of them being blank if that category doesn't apply).
There are two main issues that are giving me second thoughts:
As I said the data needs to be put into a "proper" database schema; I can't just load it as-is. I have some thoughts as to a good data model for it, but my analysis is not completed yet. There would end up being a large amount of joins tables to link various things together (e.g. products_categories, products_attributes, products_prices) etc and these tables would link products not via an ID but by their SKU (see below).
Everything already has an ID that's generated for it, but anything new I add needs to have one autogenerated; I doubt this will be a problem with any mature RDBMS, but I know Rails likes to generate IDs itself. Also, almost all of the product-related tables are linked by SKUs (and in the data provided by the supplier are actually a composite key consisting of the prefix and stock number, which combined make up the full SKU), not by IDs and I'm not sure if this will be a performance issue (of course, I could always manually create indexes on these columns to speed it up). It does mean that I'll need to break away from the Rails conventions, however.
In short, I think that Rails might be a good choice as far as time-to-market and ease-of-development, but having to work with the existing data content might turn into a pain because the application will need to be developed around that, instead of the "traditional" Rails app, and that factor is giving me major doubts about using Rails. There are also some other issues (having to set up a Linux server, and the fact that the area I live in has very few Rails developers so if I left the company I'd basically be holding them hostage as far as updates/modifications). I'm really unsure as to the best path to proceed.
I would develop the app as if you didn't have the data. Use the ORM and make your database the best it can be, but of course keep in mind what data you have to populate it with (eg: don't make crazy new constraints for things that will leave you going through old data record by record).
When you're done and tested, write an import script that pulls your real data onto your new database.
It's not that different from the conventional design/development model... Apart from you can do your data-input in a semi-automated fashion.
I was in the same situation not too long ago — a crappy PHP app that held ten years worth of all company data.
What I did was simply create a Migration model and added methods to import each resource.
class Migration
def migration_all
self.jobs
end
def self.jobs
...
end
end
The cool thing about this is that you can arrange which order resources are imported as one will likely reference another. I also added methods that directly modified the db schema. One nice trick if you have to keep an existing primary key is to create a field named 'legacy_id', copy over your existing primary key, and when you're done, simply remove the 'id' field, rename the 'legacy_id' field to 'id', then add the primary_key constraint on the new 'id' field.
Don't use the SKU as the unique key for each product - use the standard Rails incremented id.
SKU could change as it may be misentered, etc and that would make it a nightmare to change all of the references from other tables. Put your current id in a sku column, index it and update the references in your other tables to the Rails ids.
You'd be able to do Product.find_by_sku(params[:sku]) in your controllers, set up a /products/:sku route, etc. I don't see what you'd gain (other than a headache) by using your non generated ids as the database primary keys.
I'd also suggest running your old data through your app's validations to make sure you are not loading up a bunch of inconsistencies and erros. It will help your app run smoothly and highlight existing data errors at a point where you can fix them.
Don't assume the existing data is valid just because it is already there.