I have the table "tools" and "lend".
Im using Rails3 and when i create a lend i would like it change the attribute status of the tool to 'U'.
Would this is possible?
i tried on the model lend
after_save :change_status
def change_status
tools.update_attribute(status, 'U')
end
i tried too, on the same model:
after_save :change_status
def change_status
self.tool.update_attribute(status, 'U')
end
No success or warning on debug log.
Sugestions?
Thanks! :)
What is the relationship between lend and tool? If Lend has_many tools, you will have to do something like this:
def change_status
tools.each { |tool| tool.update_attributes(status: 'U') }
end
Note also that I am using update_attributes because update_attribute (singular) will be deprecated soon.
BTW, you should create a method in Tool to update the attribute, the Lend model should not be aware about how to set a tool as loaned. Something like
def loaned!
update_attributes status: 'U'
end
Firstly, I assume that your Lend model has_many :tools
In order to be able to do something like tool.update_attribute you'll need to work with the accepts_nested_attributes_for
Take a look at these links and they will probably set you on the right path:
RailsCasts #196 Nested Model Form Part 1
Active Record Nested Attributes
Hope this helps.
Related
This is something I'm trying to do now: A has_many Bs. B has certain callbacks that need to be triggered. Just, when I save from A, I want something to be updated in Bs. Since the Bs can be 10000, I would like not to load them into memory, and still have the benefit of seeing the callbacks triggered. What is the best strategy for this?
And please, no "find_each" or any find by batches variant, I'm aware of them and they will be my last resort in case nothing else works.
When I encountered this problem, I use this solution
define "callback methods" in a class and use they with ids,
define really callbacks in a instance and pass id of record in "class callback"
example of code:
class Post < AR
has_many :comments
after_save do |post|
Post.recalculate_counters(post.comment_ids)
end
end
class Comment < AR
belongs_to :post
after_save :recalculate_couters
def self.recalculate_couters(ids)
... huge and slow update statement ...
end
def recalcuate_couters
self.class.recalculate_couters([id])
end
end
I don't think there's any way you can have the callbacks executed without loading the models. However, if you give up using callback you can use update_all that performs really fast.
You just use:
B.update_all({:timestamp => Time.now}, { :a_id => id })
I am using paper trail to audit changes to data and would like to store the user_id of the current user in addition to the "whodunnit" column that paper_trail stores by default.
I had no trouble modifying the versions migration to add the user_id column. But I haven't figured out an easy way to set that column from the various models in my app.
It seems like this should work:
has_paper_trail :meta => { :user_id => current_user.id
}
And, I think it might work if I had access to the current_user in my models. But I don't. After researching how to get access to the current_user in my model, I see there is a philosophical debate here. That's not my question though.
So I'm thinking of using a gem like sentient_user or sentient_model to give me access to the current_user in my models so I can set it with something like the code above.
However, adding these gems seems complicated for the little thing I'm trying to do here. I'm wondering if there is an easier way.
What is the easiest way to add the user_id of the person who took the action to the versions table?
The current_user don't exists in models by itself, it appears from controller. So, standard approach is applicable:
class ApplicationController < ActionController::Base
def user_for_paper_trail
current_user if user_signed_in?
end
def info_for_paper_trail
{ user_id: current_user.id } if user_signed_in?
end
end
# config/initializers/paper_trail.rb
class Version < ActiveRecord::Base
attr_accessible :user_id
end
I am dealing with numerous calculations to bring various values within a model to a simple TRUE or FALSE. Problem is, these calculations are pretty intense and not something I want to create a long, hard to follow SQL statement for. I'd rather just have the entire calculation within a method that the model could check for when returning records.
I've tried numerous ways to accomplish this, and when looking up other similar feats, others push newbs like me to SQL which might serve most purposes but will not serve mine as the calculations being done are somewhat external to the model.
Model:
class Quality < ActiveRecord::Base
...
def passed_inspection
[code that calculates based on values in model]
end
Controller:
#records = Quality.where('passed_inspection = true')
View:
Did pass inspection?: <%= record.passed_inspection %>
It sounds like the solution to your problem would be to use a Scope with a Class Method to help clean up your model. Essentially you would set up your model like this:
class Quality < ActiveRecord::Base
def self.passed_inspection
# Code that does your calculations
end
scope :passed, passed_inspection() # This needs to be below the function above
end
Then you could get this data by calling it like this
#records = Quality.passed
There is a rails cast about this problem if you need any more information: RailsCast #215 Advanced Queries
Edit: Fixed some terrible grammar
I have a table that I'd like to keep pruned to the 500 most recent rows. What's the most efficient way to do this in rails?
One way to do it:
class MyModel
after_create do
self.class.prune(500)
end
def self.prune(max)
if count > max
order('created_at DESC').offset(max).each do |model|
model.destroy
end
end
end
end
The prune class method could also be added to ActiveRecord::Base if you want to use that on multiple models.
This is definitely one way to do it, although someone may chime in with a more efficient way. Create a method in your controller, for this example I'll call it "prune", and call it after your create action (there may be an after_filter or something similar you can use.) It should look something like this.
def prune
if MyModel.count > 500
#models = MyModel.all(:offset => 500)
#models.each do |m|
m.destroy!
end
end
end
A basic solution would be to use the following script under a scheduling application like whenever https://github.com/javan/whenever to run the following command :
Mould.order('updated_at DESC').offset(20).each {|m| m.destroy }
Substitute Mould with the name of your model. Usage of cron and scheduling has been discussed in detail in following post : A cron job for rails: best practices?
I have a rails app (running on version 2.2.2) that has a model called Product. Product is in a has-and-belongs-to-many relationship with Feature. The problem is that I need have search functionality for the products. So I need to be able to search for products that have a similar name, and some other attributes. The tricky part is that the search must also return products that have the exact set of features indicated in the search form (this is represented by a bunch of checkboxes). The following code works, but it strikes me as rather inefficient:
#products = Product.find(:all, :conditions=>["home=? AND name LIKE ? AND made_by LIKE ? AND supplier LIKE ? AND ins LIKE ?",hme,'%'+opts[0]+'%','%'+opts[1]+'%','%'+opts[3]+'%','%'+opts[4]+'%'])
#see if any of these products have the correct features
if !params[:feature_ids].nil?
f = params[:feature_ids].collect{|i| i.to_i}
#products.delete_if {|x| x.feature_ids!=f}
end
I'm sorry that my grasp of rails/sql is so weak, but does anyone have any suggestions about how to improve the above code? Thanks so much!
First, i would recommend you to manually write a FeatureProduct model (and not use the default 'has_and_belongs_to_many')
EG
class FeatureProduct
belongs_to :feature
belongs_to :product
end
class Product
has_many :feature_products
has_many :features, :through => :feature_products
end
class Feature
has_many :feature_products
has_many :products, :through => :feature_products
end
For the search: You may find the gem SearchLogic to be exactly what you need. It has support for 'LIKE' conditions (it means that you can write in a more 'Rails way' your query). It also has support for performing a search with conditions on a related model (on your Feature model, to be more precise).
The solution would be something like:
search = Product.search
search.name_like = opt[0]
search.made_by_like = opt[1]
...
search.feature_products_id_equals = your_feature_ids
..
#product_list = search.all
There is also an excellent screencast explaining the use of this gem.
Good luck :)