Say I have something like this in my controller:
FacultyMembership.update(params[:faculty_memberships].keys,
params[:faculty_memberships].values)
and whenever the _destroy key in params[:faculty_memberships].values is true, the record is destroyed.
Is there something like this in rails? I realize there are other ways of doing this, I was just curious if something like this existed.
Short answer
no!
Long answer
Still no! It is true that it works on nested attributes:
If you want to destroy the associated model through the attributes
hash, you have to enable it first using the :allow_destroy option.
Now, when you add the _destroy key to the attributes hash, with a
value that evaluates to true, you will destroy the associated model.
But why not trying it out in the console:
?> bundle exec rails c
?> m = MyModel.create attr_1: "some_value", attr_2: "some_value"
?> m.update(_destroy: '1') # or _destroy: true
?> ActiveRecord::UnknownAttributeError: unknown attribute '_destroy' for MyModel
This is because the update implementation is the following:
# File activerecord/lib/active_record/persistence.rb, line 245
def update(attributes)
# The following transaction covers any possible database side-effects of the
# attributes assignment. For example, setting the IDs of a child collection.
with_transaction_returning_status do
assign_attributes(attributes)
save
end
end
and the source for assign_attributes is:
# File activerecord/lib/active_record/attribute_assignment.rb, line 23
def assign_attributes(new_attributes)
if !new_attributes.respond_to?(:stringify_keys)
raise ArgumentError, "When assigning attributes, you must pass a hash as an argument."
end
return if new_attributes.blank?
attributes = new_attributes.stringify_keys
multi_parameter_attributes = []
nested_parameter_attributes = []
attributes = sanitize_for_mass_assignment(attributes)
attributes.each do |k, v|
if k.include?("(")
multi_parameter_attributes << [ k, v ]
elsif v.is_a?(Hash)
nested_parameter_attributes << [ k, v ]
else
_assign_attribute(k, v)
end
end
assign_nested_parameter_attributes(nested_parameter_attributes) unless nested_parameter_attributes.empty?
assign_multiparameter_attributes(multi_parameter_attributes) unless multi_parameter_attributes.empty?
end
This code worked for me:
class FacultyMembership < ApplicationRecord
attr_accessor :_destroy
def _destroy= value
self.destroy if value.present?
end
end
Possibly this can break nested forms with destroy - didn't check.
Related
As far as I've tested it, this helper method works exactly as it's meant to, however I want to know if there is any easier, built-in, or smarter way to run this check! I also am aware that having this in the ApplicationHelper probably isn't ideal. Not sure if I should just put it in the parent object (the Inspection), some other model, or leave as is.
With is_model_empty? I need to run through every field of any one of eleven different (but similar) models to check to see if all of them are Empty. All of them except the :id, :inspection_id, :created_at, and :updated_at fields which will never be blank. Empty can be nil, can be [], or can be ['']. An empty string would actually imply that the user entered something so that won't be included. The value can be either a string or an array so .empty? won't work.
def is_model_empty?(model)
model.attributes.each do |k, v|
unless ['id', 'inspection_id', 'created_at', 'updated_at'].include?(k)
return false unless v.nil? || v == [] || v == [""]
end
end
true
end
The eleven models all belong to the Inspection and each has a has_one relationship:
has_one :first_info_section
has_one :second_info_section
has_one :third_info_section
Any advice/feedback would be much appreciated. Thanks for reading!
-Dave
Your method can be simplifed as an instance method on each of the models. If the attribute exceptions are the same for all the models you can create a shared library and include it each of the models.
app/models/empty_detection.rb:
module EmptyDetection
def empty?
attributes.all? do |k, v|
['id', 'inspection_id', 'created_at', 'updated_at'].include?(k) || v.nil? || v == [] || v == [""]
end
end
end
Include that module in each model you want to be able to check for the empty conditions. For example, the Widget model:
class Widget < ActiveRecord::Base
include EmptyDetection
end
Now you can use it on any instance of a Widget:
widget = Widget.find(45)
widget.empty?
Here's a really basic refactor:
def is_empty?(model)
whitelist = %w[ id inspection_id created_at updated_at ]
model.attributes.all? do |attr, val|
whitelist.exclude?(attr) || val.nil? || val == [] || val == [""]
end
end
What you really want, though, is a validator, which is described in the Active Record Validations Rails Guide:
In this case it would look like this:
class EmptyValidator < ActiveModel::Validator
WHITELIST = %w[ id inspection_id created_at updated_at ].freeze
def validate(record)
return unless model.attributes.all? do |attr, val|
WHITELIST.exclude?(attr) || empty?(val)
end
record.errors[:base] << "You missed one!"
end
private
def empty?(val)
val.nil? || val == [] || val == [""]
end
end
Then, in each of your models...
class MyModel < ActiveRecord::Base
validates_with EmptyValidator
end
I hope that's helpful!
user.attributes.values.all?(&:blank?)
I have a mongoid object:
post = Post.first
When I try:
post.attributes.each do |a|
...
end
this block parse all object attributes.
I need only parse 3 attributes. post.attr1, post.attr2, post.attr3.
whitelist = %w(attr attr2 attr3)
post.attributes.select{|el| whitelist.include?(el)}.each do |key, value|
...
end
As usual, try to abstract this.
post.attributes.except("id", "created_at", "updated_at").each do |attr|
....
end
This will also help.
You could try using the only method which returns only the attributes specified (it also adds the "_id" field), for instance:
post = Post.only(:attr_1,:attr_2).first # This will give you something like => {"_id"=>"50cf2e893428ed5437000002", "attr_1"=>value, "attr_2"=>2012-12-21 02:00:00 UTC}
post.attributes.each do |a|
next if a.first == "_id" # each `a` is an array, for instance: ["_id", "50cf2e893428ed5437000002"]
#do something with the attributes
end
I have a simple relationship:
class Item
belongs_to :container, :counter_cache => true
end
class Container
has_many :items
end
Let's say I have two containers. I create an item and associate it with the first container. The counter is increased.
Then I decide to associate it with the other container instead. How to update the items_count column of both containers?
I found a possible solution at http://railsforum.com/viewtopic.php?id=39285 .. however I'm a beginner and I don't understand it. Is this the only way to do it?
It should work automatically. When you are updating items.container_id it will decreament old container's counter and increament new one. But if it isn't works - it is strange. You can try this callback:
class Item
belongs_to :container, :counter_cache => true
before_save :update_counters
private
def update_counters
new_container = Container.find self.container_id
old_container = Container.find self.container_id_was
new_container.increament(:items_count)
old_container.decreament(:items_count)
end
end
UPD
To demonstrate native behavior:
container1 = Container.create :title => "container 1"
#=> #<Container title: "container 1", :items_count: nil>
container2 = Container.create :title => "container 2"
#=> #<Container title: "container 2", :items_count: nil>
item = container1.items.create(:title => "item 1")
Container.first
#=> #<Container title: "container 1", :items_count: 1>
Container.last
#=> #<Container title: "container 1", :items_count: nil>
item.container = Container.last
item.save
Container.first
#=> #<Container title: "container 1", :items_count: 0>
Container.last
#=> #<Container title: "container 1", :items_count: 1>
So it should work without any hacking. From the box.
Modified it a bit to handle custom counter cache names
(Don't forget to add after_update :fix_updated_counter to the models using counter_cache)
module FixUpdateCounters
def fix_updated_counters
self.changes.each { |key, (old_value, new_value)|
# key should match /master_files_id/ or /bibls_id/
# value should be an array ['old value', 'new value']
if key =~ /_id/
changed_class = key.sub /_id$/, ''
association = self.association changed_class.to_sym
case option = association.options[ :counter_cache ]
when TrueClass
counter_name = "#{self.class.name.tableize}_count"
when Symbol
counter_name = option.to_s
end
next unless counter_name
association.klass.decrement_counter(counter_name, old_value) if old_value
association.klass.increment_counter(counter_name, new_value) if new_value
end
} end end
ActiveRecord::Base.send(:include, FixUpdateCounters)
For rails 3.1 users.
With rails 3.1, the answer doesn't work.
The following works for me.
private
def update_counters
new_container = Container.find self.container_id
Container.increment_counter(:items_count, new_container)
if self.container_id_was.present?
old_container = Container.find self.container_id_was
Container.decrement_counter(:items_count, old_container)
end
end
here is an approach that works well for me in similar situations
class Item < ActiveRecord::Base
after_update :update_items_counts, if: Proc.new { |item| item.collection_id_changed? }
private
# update the counter_cache column on the changed collections
def update_items_counts
self.collection_id_change.each do |id|
Collection.reset_counters id, :items
end
end
end
additional information on dirty object module http://api.rubyonrails.org/classes/ActiveModel/Dirty.html and an old video about them http://railscasts.com/episodes/109-tracking-attribute-changes and documentation on reset_counters http://apidock.com/rails/v3.2.8/ActiveRecord/CounterCache/reset_counters
Updates to #fl00r Answer
class Container
has_many :items_count
end
class Item
belongs_to :container, :counter_cache => true
after_update :update_counters
private
def update_counters
if container_id_changed?
Container.increment_counter(:items_count, container_id)
Container.decrement_counter(:items_count, container_id_was)
end
# other counters if any
...
...
end
end
I recently came across this same problem (Rails 3.2.3). Looks like it has yet to be fixed, so I had to go ahead and make a fix. Below is how I amended ActiveRecord::Base and utilize after_update callback to keep my counter_caches in sync.
Extend ActiveRecord::Base
Create a new file lib/fix_counters_update.rb with the following:
module FixUpdateCounters
def fix_updated_counters
self.changes.each {|key, value|
# key should match /master_files_id/ or /bibls_id/
# value should be an array ['old value', 'new value']
if key =~ /_id/
changed_class = key.sub(/_id/, '')
changed_class.camelcase.constantize.decrement_counter(:"#{self.class.name.underscore.pluralize}_count", value[0]) unless value[0] == nil
changed_class.camelcase.constantize.increment_counter(:"#{self.class.name.underscore.pluralize}_count", value[1]) unless value[1] == nil
end
}
end
end
ActiveRecord::Base.send(:include, FixUpdateCounters)
The above code uses the ActiveModel::Dirty method changes which returns a hash containing the attribute changed and an array of both the old value and new value. By testing the attribute to see if it is a relationship (i.e. ends with /_id/), you can conditionally determine whether decrement_counter and/or increment_counter need be run. It is essnetial to test for the presence of nil in the array, otherwise errors will result.
Add to Initializers
Create a new file config/initializers/active_record_extensions.rb with the following:
require 'fix_update_counters'
Add to models
For each model you want the counter caches updated add the callback:
class Comment < ActiveRecord::Base
after_update :fix_updated_counters
....
end
Here the #Curley fix to work with namespaced models.
module FixUpdateCounters
def fix_updated_counters
self.changes.each {|key, value|
# key should match /master_files_id/ or /bibls_id/
# value should be an array ['old value', 'new value']
if key =~ /_id/
changed_class = key.sub(/_id/, '')
# Get real class of changed attribute, so work both with namespaced/normal models
klass = self.association(changed_class.to_sym).klass
# Namespaced model return a slash, split it.
unless (counter_name = "#{self.class.name.underscore.pluralize.split("/")[1]}_count".to_sym)
counter_name = "#{self.class.name.underscore.pluralize}_count".to_sym
end
klass.decrement_counter(counter_name, value[0]) unless value[0] == nil
klass.increment_counter(counter_name, value[1]) unless value[1] == nil
end
}
end
end
ActiveRecord::Base.send(:include, FixUpdateCounters)
Sorry I don't have enough reputation to comment the answers.
About fl00r, I may see a problem if there is an error and save return "false", the counter has already been updated but it should have not been updated.
So I'm wondering if "after_update :update_counters" is more appropriate.
Curley's answer works but if you are in my case, be careful because it will check all the columns with "_id". In my case it is automatically updating a field that I don't want to be updated.
Here is another suggestion (almost similar to Satish):
def update_counters
if container_id_changed?
Container.increment_counter(:items_count, container_id) unless container_id.nil?
Container.decrement_counter(:items_count, container_id_was) unless container_id_was.nil?
end
end
My models look like the following:
class Template < ActiveRecord::Base
has_many :template_strings
accepts_nested_attributes_for :template_strings
end
class TemplateString < ActiveRecord::Base
belongs_to :template
end
The TemplateString model is identified by a compound key, on language_id and template_id (it currently has an id primary key as well, but that can be removed if necessary).
Because I am using accepts_nested_attributes_for, I can create new strings at the same time I am creating a new template, which works as it should. However, when I try to update a string in an existing template, accepts_nested_attributes_for tries to create new TemplateString objects, and then the database complains that the unique constraint has been violated (as it should).
Is there any way to get accepts_nested_attributes_for to use a compound key when determining if it should create a new record or load an existing one?
The way I solved this problem was to monkey patch accepts_nested_attributes_for to take in a :key option, and then assign_nested_attributes_for_collection_association and assign_nested_attributes_for_one_to_one_association to check for an existing record based on those key attributes, before continuing on as normal if not found.
module ActiveRecord
module NestedAttributes
class << self
def included_with_key_option(base)
included_without_key_option(base)
base.class_inheritable_accessor :nested_attributes_keys, :instance_writer => false
base.nested_attributes_keys = {}
end
alias_method_chain :included, :key_option
end
module ClassMethods
# Override accepts_nested_attributes_for to allow for :key to be specified
def accepts_nested_attributes_for_with_key_option(*attr_names)
options = attr_names.extract_options!
options.assert_valid_keys(:allow_destroy, :reject_if, :key)
attr_names.each do |association_name|
if reflection = reflect_on_association(association_name)
self.nested_attributes_keys[association_name.to_sym] = [options[:key]].flatten.reject(&:nil?)
else
raise ArgumentError, "No association found for name `#{association_name}'. Has it been defined yet?"
end
end
# Now that we've set up a class variable based on key, remove it from the options and call
# the overriden method to continue setup
options.delete(:key)
attr_names << options
accepts_nested_attributes_for_without_key_option(*attr_names)
end
alias_method_chain :accepts_nested_attributes_for, :key_option
end
private
# Override to check keys if given
def assign_nested_attributes_for_one_to_one_association(association_name, attributes, allow_destroy)
attributes = attributes.stringify_keys
if !(keys = self.class.nested_attributes_keys[association_name]).empty?
if existing_record = find_record_by_keys(association_name, attributes, keys)
assign_to_or_mark_for_destruction(existing_record, attributes, allow_destroy)
return
end
end
if attributes['id'].blank?
unless reject_new_record?(association_name, attributes)
send("build_#{association_name}", attributes.except(*UNASSIGNABLE_KEYS))
end
elsif (existing_record = send(association_name)) && existing_record.id.to_s == attributes['id'].to_s
assign_to_or_mark_for_destruction(existing_record, attributes, allow_destroy)
end
end
# Override to check keys if given
def assign_nested_attributes_for_collection_association(association_name, attributes_collection, allow_destroy)
unless attributes_collection.is_a?(Hash) || attributes_collection.is_a?(Array)
raise ArgumentError, "Hash or Array expected, got #{attributes_collection.class.name} (#{attributes_collection.inspect})"
end
if attributes_collection.is_a? Hash
attributes_collection = attributes_collection.sort_by { |index, _| index.to_i }.map { |_, attributes| attributes }
end
attributes_collection.each do |attributes|
attributes = attributes.stringify_keys
if !(keys = self.class.nested_attributes_keys[association_name]).empty?
if existing_record = find_record_by_keys(association_name, attributes, keys)
assign_to_or_mark_for_destruction(existing_record, attributes, allow_destroy)
return
end
end
if attributes['id'].blank?
unless reject_new_record?(association_name, attributes)
send(association_name).build(attributes.except(*UNASSIGNABLE_KEYS))
end
elsif existing_record = send(association_name).detect { |record| record.id.to_s == attributes['id'].to_s }
assign_to_or_mark_for_destruction(existing_record, attributes, allow_destroy)
end
end
end
# Find a record that matches the keys
def find_record_by_keys(association_name, attributes, keys)
[send(association_name)].flatten.detect do |record|
keys.inject(true) do |result, key|
# Guess at the foreign key name and fill it if it's not given
attributes[key.to_s] = self.id if attributes[key.to_s].blank? and key = self.class.name.underscore + "_id"
break unless (record.send(key).to_s == attributes[key.to_s].to_s)
true
end
end
end
end
end
Perhaps not the cleanest solution possible, but it works (note that the overrides are based on Rails 2.3).
I have an object now:
class Items
attr_accessor :item_id, :name, :description, :rating
def initialize(options = {})
options.each {
|k,v|
self.send( "#{k.to_s}=".intern, v)
}
end
end
I have it being assigned as individual objects into an array...
#result = []
some loop>>
#result << Items.new(options[:name] => 'name', options[:description] => 'blah')
end loop>>
But instead of assigning my singular object to an array... how could I make the object itself a collection?
Basically want to have the object in such a way so that I can define methods such as
def self.names
#items.each do |item|
item.name
end
end
I hope that makes sense, possibly I am overlooking some grand scheme that would make my life infinitely easier in 2 lines.
A few observations before I post an example of how to rework that.
Giving a class a plural name can lead to a lot of semantic issues when declaring new objects, as in this case you'd call Items.new, implying you're creating several items when in fact actually making one. Use the singular form for individual entities.
Be careful when calling arbitrary methods, as you'll throw an exception on any misses. Either check you can call them first, or rescue from the inevitable disaster where applicable.
One way to approach your problem is to make a custom collection class specifically for Item objects where it can give you the information you need on names and such. For example:
class Item
attr_accessor :item_id, :name, :description, :rating
def initialize(options = { })
options.each do |k,v|
method = :"#{k}="
# Check that the method call is valid before making it
if (respond_to?(method))
self.send(method, v)
else
# If not, produce a meaningful error
raise "Unknown attribute #{k}"
end
end
end
end
class ItemsCollection < Array
# This collection does everything an Array does, plus
# you can add utility methods like names.
def names
collect do |i|
i.name
end
end
end
# Example
# Create a custom collection
items = ItemsCollection.new
# Build a few basic examples
[
{
:item_id => 1,
:name => 'Fastball',
:description => 'Faster than a slowball',
:rating => 2
},
{
:item_id => 2,
:name => 'Jack of Nines',
:description => 'Hypothetical playing card',
:rating => 3
},
{
:item_id => 3,
:name => 'Ruby Book',
:description => 'A book made entirely of precious gems',
:rating => 1
}
].each do |example|
items << Item.new(example)
end
puts items.names.join(', ')
# => Fastball, Jack of Nines, Ruby Book
Do you know the Ruby key word yield?
I'm not quite sure what exactly you want to do. I have two interpretations of your intentions, so I give an example that makes two completely different things, one of them hopefully answering your question:
class Items
#items = []
class << self
attr_accessor :items
end
attr_accessor :name, :description
def self.each(&args)
#items.each(&args)
end
def initialize(name, description)
#name, #description = name, description
Items.items << self
end
def each(&block)
yield name
yield description
end
end
a = Items.new('mug', 'a big cup')
b = Items.new('cup', 'a small mug')
Items.each {|x| puts x.name}
puts
a.each {|x| puts x}
This outputs
mug
cup
mug
a big cup
Did you ask for something like Items.each or a.each or for something completely different?
Answering just the additional question you asked in your comment to tadman's solution: If you replace in tadman's code the definition of the method names in the class ItemsCollection by
def method_missing(symbol_s, *arguments)
symbol, s = symbol_s.to_s[0..-2], symbol_s.to_s[-1..-1]
if s == 's' and arguments.empty?
select do |i|
i.respond_to?(symbol) && i.instance_variables.include?("##{symbol}")
end.map {|i| i.send(symbol)}
else
super
end
end
For his example data you will get following outputs:
puts items.names.join(', ')
# => Fastball, Jack of Nines, Ruby Book
puts items.descriptions.join(', ')
# => Faster than a slowball, Hypothetical playing card, A book made entirely of precious gems
As I don't know about any way to check if a method name comes from an attribute or from another method (except you redefine attr_accessor, attr, etc in the class Module) I added some sanity checks: I test if the corresponding method and an instance variable of this name exist. As the class ItemsCollection does not enforce that only objects of class Item are added, I select only the elements fulfilling both checks. You can also remove the select and put the test into the map and return nil if the checks fail.
The key is the return value. If not 'return' statement is given, the result of the last statement is returned. You last statement returns a Hash.
Add 'return self' as the last line of initialize and you're golden.
Class Item
def initialize(options = {})
## Do all kinds of stuff.
return self
end
end