In Ryan Bates's first episode on complex forms, he adds the following to a model:
# models/project.rb
has_many :tasks
def task_attributes=(task_attributes)
task_attributes.each do |attributes|
tasks.build(attributes)
end
end
I've never thought about this before, but how does the Project model know what "tasks" of which Project instance? Does that come from the has_many association? Is it like, when the project is running and I'm viewing a Project, that's the "active" object so project.rb knows which Project object we're referring to, so it knows that tasks is really some_current_project.tasks? (I'm obviously grasping at straws here.)
Also, if someone would point me to some reference that explains other questions like this one, I'd really appreciate it.
I hope my question is clear. Please ask for more clarification in comments if needed.
Please note: I know that Active Record handles CRUD actions and that objects correspond to rows in tables, etc. Those are just descriptions of what Active Record is. I'm looking for how it works when the project is running. I also now the constructs MVC, but I can't seem to find a detailed explanation of what information is sent where with respect to Rails.
(Not sure I fully understood your question, feel free to let me know if that's the case.)
A rails model is basically a ruby class that is persisted to a database. So it acts like a normal ruby object for the most part, with some database magic mixed in.
You tell rails which project instance to load (e.g. by providing an id), and it loads the data from the database.
Then, when you call project.tasks is when the magic happens: the Project model has no tasks method, so it will trigger ruby's method_missing method. This will then load the associated records into model instances and provide access to them via a rails object.
Since a project has many tasks, rails knows it should look into the tasks database and load the rows where project_id is equal to the project model's id attribute.
In short, ruby meta-programming and monkey patching possibilities make much of rails' magic possible.
(Edit for question on routing.)
When you want to edit project number 13, you go to a URL that looks something like www.mysite.com/projects/13/edit. If you look at routes.rb in your config directory, you'll see (in Rails3) resources :projects what Rails does is set up all sorts of paths for you. Behind the magic, the edit path looks like
get '/projects/:id/edit' => 'projects#edit'
This basically says "when a user wants to see www.mysite.com/projects/13/edit, send him to the edit action in the projects controller and set the id parameter to the value that's in that place.
Then in your controller, you'll load the appropriate project with
#project = Project.find(params[:id])
In a similar way, you could do this (this is an dumb example):
In routes.rb, put
get '/projects/:id/edit_name/:name' => 'projects#edit'
And then in you controller
#project = Project.find(params[:id])
#project.name = params[:name]
So rails basically uses magic to assign values in the URL to params you can work with in your controller. You can read more about routing here: http://guides.rubyonrails.org/routing.html
Related
delete_all is useful, but I never want to see it called on the same line with a table name. I'd like to disable things like TableName.destroy_all in both console and code.
One interesting issue happened earlier this month:
Application.destroy_all was called on a model instead of applications.destroy_all
(the model has_many applications)
For somebody new to ROR, it looks very similar, but the results were disastrous.
I'm open to some form of lint/code style tool, but that really wouldn't catch it in the console scenario. (Plus, I haven't been able to get rubo-cop to do something like this yet)
Basically, I'm asking for a way to make the console and codebase more secure so that newer developers can't inadvertantly delete everything in a table.
I'm not entirely clear on what you are trying to accomplish, but you could try overriding the method in your ApplicationModel with something like this (assuming Rails 5 or greater, or otherwise a root model in existence).
class ApplicationModel < ActiveRecord::Base
def self.destroy_all(*args)
raise('Cannot destroy all records of a model this way. Did you mean to delete a subset of records instead?')
end
end
Possibly make this method private if you'd like it even harder to run...
def self.destroy_all(*args)
raise('Cannot destroy all records of a model this way. Did you mean to delete a subset of records instead?')
end
private_class_method :destroy_all
You could get fancy and allow this to be bypassed with a special argument that you check for, but give this a try and see how it goes.
I am new to polymorphic associations and am a bit lost at the moment.
I am trying to add a functionality to my website where users can ask quotes to different types of professionnals. Each professionnal own a specific type of quote such as :
model photographer own photographerquotes
I did this because each type of quotes is very dependable to the professional model it belongs to, and database model is specific for each.
Though one thing is constant with those quotes models : they can be commented either by the user or the professionnal
I have then made the different quotes models commentable but I am a bit lost when I need to create the commentable variable inside the comments controller #create action.
this tutorial says we can make modules https://gorails.com/episodes/comments-with-polymorphic-associations (at 15:00)
And the railscast here: https://www.youtube.com/watch?v=WOFAcbxdWjY grabs the correct quote model directly from the address bar with his following trick :
def load_commentable
klass = [Article, Photo, Event].detect { |c| params["#{c.name.underscore}_id"] }
#commentable = klass.find(params["#{klass.name.underscore}_id"])
end
actually both seem counterintuitive to me as I am no Ruby expert, nor even Rails expert yet.
Is one of the two solutions a desired solution ? Are there some more possibilities in 2017 developping under rails 5 ?
EDIT
Actually there would be a third possibility :
it is to pass the quote model type and id inside the form as hidden fields. But it the gorails tutorial the person says that anybody can pass these data for us and this is not really safe ...
I am no HTPP expert but I thought the CREATE method couldnt be replicated inside the address bar. I thought only the GET method was 'public'...
I know this is probably an extremely basic level question, but I'm new to rails and can't seem to locate a clear answer in the Ruby Guides on my own; it's likely that I just don't know the term for this and can't figure it out.
I've got two models, documents and companies (companies is a table built by devise). Companies has_many :documents and documents belongs_to :companies. On my form there is a place for the company's name, address, etc., and I would like to populate the associated company on both on the _form.html.erb and the show.html.erb so that it's not necessary to input this information every time you fill out a form. It's not absolutely necessary that the information be present on the _form.html.erb, but it would be nice to go ahead and present this information so as to not confuse the user.
When I try calling #companies.company_name in my documents show view, I hit a nil class error. I've tried adding #companies = companies.all to my controller, but that doesn't work either. Like I said, I'm sure this is a simple problem, but I don't have much hair left and would like to preserve it for another problem.
I was able to find a different method that seems to be working well at the moment. Instead of adding #company = Company.find (params[:id]), I was able to call #document.company.company_name within the show action. I'll forgo to the new and edit for the moment since show was all that mattered.
I know the dogma says to not access current_user in a model but I don't fully agree with it. For example, I want to write a set of logging functions when an action happens via a rails callback. Or simply writing who wrote a change when an object can have multiple people write to it (not like a message which has a single owner). In many ways, I see current_user more as config for an application - in other words make this app respond to this user. I would rather have my logging via the model DSL rather than in the action where it seems REALLY out of place. What am I missing?
This idea seems rather inelegant Access current_user in model
as does this: http://rails-bestpractices.com/posts/47-fetch-current-user-in-models
thx
edit #1
So my question isn't if there are gems that can do auditing / logging. I currently use paper_trail (although moving away from it because I can do same functionality in approx 10 lines of ruby code); it is more about whether current_user should never be accessed in the model - I essentially want to REDUCE my controller code and push down logic to models where it should be. Part of this might be due to the history of ActiveRecord which is essentially a wrapper around database tables for which RoR has added a lot of functionality over the years.
You've given several examples that you'd like to accomplish, I'll go through the solution to each one separately:
I want to write a set of logging functions when an action happens via
a rails callback
Depending on how you want to log (DB vs writing to the logger). If you want to log to the DB, you should have a separate logging model which is given the appropriate information from the controller, or simply with a belongs_to :user type setup. If you want to write to the logger, you should create a method in your application controller which you can call from your create and update methods (or whatever other actions you wanted to have a callback on.)
Or simply writing who wrote a change when an object can have multiple people write to it
class Foo < ActiveRecord::Base
belongs_to :user, as: :edited_by
end
class FooController < ApplicationController
def update
#foo = Foo.find(params[:id])
#foo.attributes = params[:foo]
#foo.edited_by = current_user
end
end
I think you're misunderstanding what the model in Rails does. Its scope is the database. The reason it can't access current_user, is because the current user is not stored in the database, it is a session variable. This has absolutely nothing to do with the model, as this is something that can not exist without a browser.
ActiveRecord::Base is not a class that is designed to work with the browser, it is something that works with the database and only the database. You are using the browser as an interface to that model, but that layer is what needs to access browser specific things such as session variables, as your model is extending a class that is literally incapable of doing so.
This is not a dogma or style choice. This is a fact of the limitations of the class your model is extending from. That means your options basically boil down to extending from something else, handling it in your controller layer, or passing it to the model from your controller layer. ActiveRecord will not do what you want in this case.
The two links you show (each showing imho the same approach) is very similar to a approach I still use. I store the current_user somewhere (indeed thread-context is the safest), and in an observer I can then create a kind of audit-log of all changes to the watched models, and still log the user.
This is imho a really clean approach.
An alternative method, which is more explicit, less clean but more MVC, is that you let the controller create the audit-log, effectively logging the actions of the users, and less the effects on different models. This might also be useful, and in one website we did both. In a controller you know the current-user, and you know the action, but it is more verbose.
I believe your concerns are that somehow this proposed solution is not good enough, or not MVC enough, or ... what?
Another related question: How to create a full Audit log in Rails for every table?
Also check out the audited gem, which solves this problem as well very cleanly.
Hope this helps.
I'm still new to ROR, so pardon the simplicity of the question...
So http://www.example.com/controller/:id displays a record in my table, with :id being a number (1,2,3 etc.).
Is there a way I can have :id in the URL be the value of a field in the displayed record? Such that I can have http://www.example.com/controller/record_field? I want to have a human-friendly reference to specific records in my table. I'm sure this must be possible. Do I change something in routes.rb?
Thanks for the help!
The cleanest way is to add a new find method in your model (or simply use the find_by_fieldname Rails gives you in your control). Then you'll have your controller use that method instead of the regular find(params[:id]) to pull your model record.
Check out Ryan B's screencast on this here. It's pretty easy, and he's a good teacher, so you shouldn't have any problems.
I use the excellent rails plugin named friendly_id.
http://github.com/norman/friendly_id/tree/master
That should sort you out nicely. It is well documented too.
Take care around fields that might have modern Greek characters—might need to figure a work around for those.
Jon Smock's solution will work, too. I tend to prefer the following.
class Hamburger << ActiveRecord::Base
#this normally defaults to id
def to_param
name
end
end
class SomeModelController << ApplicationController
def show
#hamburger = Hamburger.find(params[:id]) #still default code
end
end
#goes in some view
This is the <%= link_to "tastiest hamburger ever", url_for(#hamburger) %>.
This is, loosely speaking, an SEO technique (beautiful URLs are also user-friendly and I suggest them to absolutely everyone even if you don't care about SEO, for example on pages behind a login). I have a more extended discussion of Rails SEO, which includes other tips like this, here.
Important tip: You should consider, at design-time, what you are going to do if the param should change. For example, in my hamburger scenario, it is entirely possible that I might rename "Sinfully Delicious Cheeseburger" to "Triple Bypass". If that changes URLs, there are some possible implications, such as breakage of customer links to my website. Accordingly, for production use I usually give these models an immutable permalink attribute which I initialize to be human-meaningful exactly once. If the object later changes, oh well, the URL stays the same. (There are other solutions -- that is just the easiest one.)