In a Rails controller I'm using a JSON request to an external database to return integers that are used to order a collection of records:
Model.order(JSON.parse(open("http://myapp.com/models/#{:id}")).read)['attribute'])
I want to make this dynamic to aid switching between environments. Something like:
Model.order(JSON.parse(open(model_url(model))).read)['attribute'])
This is not correct, and model_url(model) is returning an error:
undefined local variable or method 'model'
How do I refer to self in query?
There must be a more elegant solution than
...JSON.parse(open("#{root_url}/models/{:id}"))....
EDIT:
Lightswitch05's answer below does anser the question I asked. The query should reference params[:id] to get the url of the current record.
In fact, I have decided to move this JSON call into a virtual attribute on the model. This means I can simply call Model.order(:my_virtual_attribute). While this solution brings its own share of issues—I needed to make url_helpers available to the model—in the long run I think this will be a cleaner solution.
As per our discussion the problem is that model is not defined. Since all you are trying to do with model is get the url to it, all you really need is params[:id]. This will fix your error message:
Model.order(JSON.parse(open(model_url(params[:id]))).read)['attribute'])
where model has been replaced with params[:id]
Change your code:
Model.order(JSON.parse(open(model_url(model))).read)['attribute'])
to:
model_tableized = Model.to_s.tableize
model_url = "#{model_tableized}_url(#{model_tableized.chomp('s')})"
Model.order(JSON.parse(open(model_url).read)["attribute"])
I think that should work.
You need the name method.
If you're using the model, and not an instance of the model, it would be Model.name
If you're using an instance, it would be
#model = Model.first
#model.class.name
Related
I have followed this tutorial on how to accept not-only-numeric primary key id when creating instance of my ModelName in my Ruby on Rails application.
Everything is okay, but there is a paragraph:
Be aware that Product.find won’t work anymore, and other Rails helper that relies on id will stop functioning. If you really want that, you need to override more methods and this seems too much of a pain for me. So I’d highly recommend you to leave #id as is.
The question is: when I am trying to get instance of my model by using .find() method in my ModelNameController it doesn't work (I think that's because of .find() method's search parameters - it does find something by id field which is numeric)
I have this piece of code:
def set_model_name
#model_name = ModelName.find(params[:hashid])
end
Where :hashid is a parameter that is a string (I'd like to use a string instead of a number)
How could I solve my problem?
One of the solutions would be overriding ActiveRecord::Base's .find() method.
Thanks in advance!
You do not need to override the default behaviour of find. Instead, you can use the find_by method:
def set_model_name
#model_name = ModelName.find_by(hashid: params[:hashid])
end
How can i remove the last element from an ActiveRecord_Relation in rails?
e.g. if I set:
#drivers = Driver.all
I can add a another Driver object called #new_driver to #drivers by doing:
#drivers << #new_driver
But how can I remove an object from #drivers?
The delete method doesn't seem to work, i.e.
#drivers.delete(0)
You can use the reject! method, this will remove the object from the collection without affecting the db
for example:
driver_to_delete = #driver.first # you need the object that you want removed
#drivers.reject!{|driver| driver == driver_to_delete}
Very late too, but I arrived here looking for a fast answer and finished by thinking by myself ;)
Just to clarify about the different answers and the Rails 6.1 comment on accepted answer:
The OP wanted to remove one entry from a query, but NOT remove it from database, so any answer with delete or destroy is just wrong (this WILL delete data from your database !!).
In Ruby (and therefore Rails) convention, shebang methods (ending with !) tend to alter the given parameter. So reject! would imply modifying the source list ... but an ActiveRecord_Relation is basically just a query, NOT an array of entries !
So you'd have 2 options:
Write your query differently to specifically say you don't want some id:
#drivers.where.not(id: #driver_to_remove) # This still is an ActiveRecord_Relation
Use reject (NO shebang) on your query to transform it into an Array and "manually" remove the entry you don't want:
#drivers.reject{ |driver| driver == #driver_to_remove}
# The `reject` forces the execution of the query in DB and returns an Array)
On a performance point of view, I would personally recommend the first solution as it would be just a little more complex against the DB where the latter implies looping on the whole (eventually large) array.
Late to the question, but just had the same issue and hope this helps someone else.
reject!did not work for ActiveRecord_Relation in Rails 4.2
drop(1) was the solution
In this case #drivers.drop(0) would work to drop the first element of the relation
Since its an array of objects, have you tried to write something like #drivers.delete(#new_driver) or #drivers.delete(id: #new_driver.id) ?
This is the documentation you need:
#group.avatars << Avatar.new
#group.avatars.delete(#group.avatars.last)
--
.destroy
The problem you've got is you're trying to use collection methods on a non-collection object. You'll need to use the .destroy ActiveRecord method to get rid of the record from the database (and consequently the collection):
#drivers = Driver.all
#drivers.last.destroy
--
Scope
.delete will remove the record from the DB
If you want to pull specific elements from the db to populate the #drivers object, you'll need to use a scope:
#app/models/driver.rb
Class Driver < ActiveRecord::Base
scope :your_scope, -> { where column: "value" }
end
This will allow you to call:
#app/controllers/drivers_controller.rb
def index
#drivers = Driver.your_scope
end
I think you're getting the MVC programming pattern confused - data manipulation is meant to happen in the model, not the controller
As stated above, reject! doesn't work in Rails 4.2, but delete does, so #drivers.delete(#new_driver) works, and more generally:
#drivers.delete(Driver.where(your condition))
Hi I currently have a helper method that gets Klass.all.map{|m| m.name}. Now I use ids to get the name from the array and if I add more it'll automatically update.
When I use this helper method in a loop in the view, I think it will make multiple queries to get the Klass each time which means a lot of extra work.
I was wondering how I can "cache" this array or if I should be doing this a better way.
Thanks!
SQL caching is done automatically if you're within the same action. You can see here for a more detailed explanation. Just by the way, it would probably be more efficient to use pluck, as in Klass.pluck(:name). This would optimize your SQL query.
Your helper method should look similar to this
def klass_names
#klass_names ||= Klass.all.map{|m| m.name}
end
I am trying to search my database before I enter the record, by doing this:
Product.update_or_create_by_name_and_date_and_applicationURL_and_server_and_addi_servers(app_name, app_date,url_app,server_name,addi_servers)
the problem is that I get an undefined method exception!
Is there another way to search for the same record before entering one?
You should use two steps:
#Suggestion 1
obj = Product.find_or_create_by_...
#Suggestion 2
obj = Product.find_or_initialize_by_...
obj.update_attributes hash_here
Rereading, your question, I can't really understand what do you want to update if you try to find an object with known attributes. Anyway, you would just have to adapt my answer a little if some fields are for identifying and some for update.
I would define a function in your model: something like
Product.find_by_everything
where you write out all the parameters of the search, instead of using the the long naming method.
Then, if that returns nil, create the product. This doesn't seem to be a good use case of using the built in activerecord naming methods.
I'm working on implementing a search form in a ruby on rails application. The general idea is to use form_tag to submit the search fields (via params) to a search function in the model of the class I'm trying to search. The search function will then iterate through each of the params and execute a scoping function if the name of the function appears in params.
The issue is that when I call the search on a collection like so:
#calendar.reservations.search({:search_email => "test"})
I don't know how to refer to the collection of #calendar.reservations from within the search function.
Additionally I'm confused as to why #calendar.reservations.search(...) works, but Reservations.all.search gives me an error saying you can't call an instance method on an array.
I've got the details of the search method over here: https://gist.github.com/783964
Any help would be greatly appreciated!
I don't know how to refer to the
collection of #calendar.reservations
from within the search function.
If you use self (or Reservation, it's the same object) inside the classmethod, you will access the records with the current scope, so in your case you will see only the reservations of a particular calendar.
[edit] I looked at you search function, and I think what you want is:
def self.search(search_fields)
search_fields.inject(self) do |scope, (key, value)|
scope.send(key, value)
end
end
Additionally I'm confused as to why
#calendar.reservations.search(...)
works, but Reservations.all.search
gives me an error saying you can't
call an instance method on an array.
#calendar.reservations does not return a standard array but a (lazy) AssociationCollection, where you can still apply scopes (and classmethods as your filter). On the other hand Reservation.all returns a plain array, so you cannot execute search there (or any scope, for that matter).
You don't really need a search method at all, as far as I can tell.
Simply use where:
#calendar.reservations.where(:search_email => 'test')
I would strongly encourage you to look at the MetaSearch GEM by Ernie Miller. It handles the kind of thing you're working on very elegantly and is quite easy to implement. I suspect that your view code would almost accomplish what the GEM needs already, and this would take care of all your model searching needs very nicely.
Take a look and see if it will solve your problem. Good luck!
Reservation.all.search doesn't work because it returns all the results as an array, while Reservation.where(..) returns an ActiveRecord object (AREL). Reservation.all actually fetches the results instead of just building the query further, which methods like where, limit etc do.