Is there a way to compare two instances of model like
Model.compare_by_name("model1", "model2") which would list the differing column fields
You can use ActiveRecord::Diff if you want a mapping of all the fields that differ and their values.
alice = User.create(:name => 'alice', :email_address => 'alice#example.org')
bob = User.create(:name => 'bob', :email_address => 'bob#example.org')
alice.diff?(bob) # => true
alice.diff(bob) # => {:name => ['alice', 'bob'], :email_address => ['alice#example.org', 'bob#example.org']}
alice.diff({:name => 'eve'}) # => {:name => ['alice', 'eve']}
There is no standard comparator for this. The standard ActiveModel comparator:
Returns true if comparison_object is the same exact object, or comparison_object is of the same type and self has an ID and it is equal to comparison_object.id.
You can write your own by using Hash#diff from activesupport. Something like the following should hopefully get you started:
def Model.compare_by_name(model1, model2)
find_by_name(model1).attributes.diff(find_by_name(model2).attributes)
end
Without using a library or defining a custom method, you can easily get a diff between two models.
For instance,
a = Foo.first
b = Foo.second
a.attributes = b.attributes
a.changes #=> {"id" => [1,2] }
leave_policy is table having columns :id ,:group_detail_id , employee_type_id,
I want to combination of :group_detail_id and employee_type_id should not be duplicate.
validates_uniqueness_of :employee_type_id ,:scope => :group_detail_id
this line is not working...I don't know why?????
Try:
validate :unique_combination
def unique_combination
self.class.exists?(
:employee_type_id => employee_type_id,
:group_detail_id => group_detail_id
)
end
I am trying out seeds.rb for the first time, and one of my data models uses encapsulation provided by the money gem.
Relevant gems:
money (3.6.1)
rails (3.0.5)
My model thus far:
app/models/list.rb
class List < ActiveRecord::Base
attr_accessible :alias, :unit, :participating_manufacturer, :quantity
:latest_price_cents, :latest_price_currency, :url
belongs_to :user
composed_of :latest_price,
:class_name => "Money",
:mapping => [%w(latest_price_cents latest_price_cents), %w(latest_price_currency currency_as_string)],
:constructor => Proc.new {
|latest_price_cents, latest_price_currency| Money.new(latest_price_cents ||
0, latest_price_currency || Money.default_currency)
},
:converter => Proc.new {
|value| value.respond_to?(:to_money) ? value.to_money : raise(ArgumentError,
"Can't convert #{value.class} to Money")
}
end
1) (Addressed successfully)
2) When I get to writing validations, would it be best to write them for the :latest_price attribute or for the :latest_price_cents & :latest_price_currency attributes seperately?
/db/seeds.rb
users = User.create([{ :name => "Foo", :email => "foo#gmail.com",
:password => "foobar", :password_confirmation => "foobar" }])
# etc, will add more users to the array
list = List.create(:user_id => users.first.id, :alias => "Januvia 100mg",
:unit => "tablet", :participating_manufacturer => "Merck",
:quantity => 30, :latest_price_cents => 7500,
:latest_price_currency => "USD", :url =>
"http://www.foobar.com/januvia/100mg-tablets/")
3) Perhaps it is minutiae, but in the seed, should I be assigning values to the virtual :latest_price attribute or to the latest_price_cents and latest_price_currency attributes directly? Is there any way to use faker rather than /db/seeds.rb to perform this task?
I am new to rails and web development.
I can't see your latest_price attribute anywhere, so I'm not sure how to answer your question. Generally, you should validate the attributes entered in the user form. So if a user enters latest_price_cents and latest_price_currency in a form, then they're the ones which need validating.
There's a bug in your seed file. You want to pass in a hash, not an array, when creating a new user; and users should be an array.
users = []
users << User.create!(:name => "Foo",
:email => "foo#gmail.com",
:password => "foobar",)
:password_confirmation => "foobar")
However, if you're considering faker because you want to create some dummy data, take a look at Machinist or Factory Girl. They're designed for creating dummy data, normally for automated tests.
Once you've set up some blueprints, if you want to create dummy data in your seeds file, you can do something like this in seeds.rb:
20.times { List.make } unless Rails.env.production?
Here's some of my production code (I had to force line breaks):
task = Task.find_or_create_by_username_and_timestamp_and_des \
cription_and_driver_spec_and_driver_spec_origin(username,tim \
estamp,description,driver_spec,driver_spec_origin)
Yes, I'm trying to find or create a unique ActiveRecord::Base object. But in current form it's very ugly. Instead, I'd like to use something like this:
task = Task.SOME_METHOD :username => username, :timestamp => timestamp ...
I know about find_by_something key=>value, but it's not an option here. I need all values to be unique. Is there a method that'll do the same as find_or_create_by, but take a hash as an input? Or something else with similat semantics?
Rails 3.2 first introduced first_or_create to ActiveRecord. Not only does it have the requested functionality, but it also fits in the rest of the ActiveRecord relations:
Task.where(attributes).first_or_create
In Rails 3.0 and 3.1:
Task.where(attributes).first || Task.create(attributes)
In Rails 2.1 - 2.3:
Task.first(:conditions => attributes) || Task.create(attributes)
In the older versions, you could always write a method called find_or_create to encapsulate this if you'd like. Definitely done it myself in the past:
class Task
def self.find_or_create(attributes)
# add one of the implementations above
end
end
I also extend the #wuputah's method to take in an array of hashes, which is very useful when used inside db/seeds.rb
class ActiveRecord::Base
def self.find_or_create(attributes)
if attributes.is_a?(Array)
attributes.each do |attr|
self.find_or_create(attr)
end
else
self.first(:conditions => attributes) || self.create(attributes)
end
end
end
# Example
Country.find_or_create({:name => 'Aland Islands', :iso_code => 'AX'})
# take array of hashes
Country.find_or_create([
{:name => 'Aland Islands', :iso_code => 'AX'},
{:name => 'Albania', :iso_code => 'AL'},
{:name => 'Algeria', :iso_code => 'DZ'}
])
Is there any way of overriding a model's id value on create? Something like:
Post.create(:id => 10, :title => 'Test')
would be ideal, but obviously won't work.
id is just attr_protected, which is why you can't use mass-assignment to set it. However, when setting it manually, it just works:
o = SomeObject.new
o.id = 8888
o.save!
o.reload.id # => 8888
I'm not sure what the original motivation was, but I do this when converting ActiveHash models to ActiveRecord. ActiveHash allows you to use the same belongs_to semantics in ActiveRecord, but instead of having a migration and creating a table, and incurring the overhead of the database on every call, you just store your data in yml files. The foreign keys in the database reference the in-memory ids in the yml.
ActiveHash is great for picklists and small tables that change infrequently and only change by developers. So when going from ActiveHash to ActiveRecord, it's easiest to just keep all of the foreign key references the same.
You could also use something like this:
Post.create({:id => 10, :title => 'Test'}, :without_protection => true)
Although as stated in the docs, this will bypass mass-assignment security.
Try
a_post = Post.new do |p|
p.id = 10
p.title = 'Test'
p.save
end
that should give you what you're looking for.
For Rails 4:
Post.create(:title => 'Test').update_column(:id, 10)
Other Rails 4 answers did not work for me. Many of them appeared to change when checking using the Rails Console, but when I checked the values in MySQL database, they remained unchanged. Other answers only worked sometimes.
For MySQL at least, assigning an id below the auto increment id number does not work unless you use update_column. For example,
p = Post.create(:title => 'Test')
p.id
=> 20 # 20 was the id the auto increment gave it
p2 = Post.create(:id => 40, :title => 'Test')
p2.id
=> 40 # 40 > the next auto increment id (21) so allow it
p3 = Post.create(:id => 10, :title => 'Test')
p3.id
=> 10 # Go check your database, it may say 41.
# Assigning an id to a number below the next auto generated id will not update the db
If you change create to use new + save you will still have this problem. Manually changing the id like p.id = 10 also produces this problem.
In general, I would use update_column to change the id even though it costs an extra database query because it will work all the time. This is an error that might not show up in your development environment, but can quietly corrupt your production database all the while saying it is working.
we can override attributes_protected_by_default
class Example < ActiveRecord::Base
def self.attributes_protected_by_default
# default is ["id", "type"]
["type"]
end
end
e = Example.new(:id => 10000)
Actually, it turns out that doing the following works:
p = Post.new(:id => 10, :title => 'Test')
p.save(false)
As Jeff points out, id behaves as if is attr_protected. To prevent that, you need to override the list of default protected attributes. Be careful doing this anywhere that attribute information can come from the outside. The id field is default protected for a reason.
class Post < ActiveRecord::Base
private
def attributes_protected_by_default
[]
end
end
(Tested with ActiveRecord 2.3.5)
Post.create!(:title => "Test") { |t| t.id = 10 }
This doesn't strike me as the sort of thing that you would normally want to do, but it works quite well if you need to populate a table with a fixed set of ids (for example when creating defaults using a rake task) and you want to override auto-incrementing (so that each time you run the task the table is populate with the same ids):
post_types.each_with_index do |post_type|
PostType.create!(:name => post_type) { |t| t.id = i + 1 }
end
Put this create_with_id function at the top of your seeds.rb and then use it to do your object creation where explicit ids are desired.
def create_with_id(clazz, params)
obj = clazz.send(:new, params)
obj.id = params[:id]
obj.save!
obj
end
and use it like this
create_with_id( Foo, {id:1,name:"My Foo",prop:"My other property"})
instead of using
Foo.create({id:1,name:"My Foo",prop:"My other property"})
This case is a similar issue that was necessary overwrite the id with a kind of custom date :
# in app/models/calendar_block_group.rb
class CalendarBlockGroup < ActiveRecord::Base
...
before_validation :parse_id
def parse_id
self.id = self.date.strftime('%d%m%Y')
end
...
end
And then :
CalendarBlockGroup.create!(:date => Date.today)
# => #<CalendarBlockGroup id: 27072014, date: "2014-07-27", created_at: "2014-07-27 20:41:49", updated_at: "2014-07-27 20:41:49">
Callbacks works fine.
Good Luck!.
For Rails 3, the simplest way to do this is to use new with the without_protection refinement, and then save:
Post.new({:id => 10, :title => 'Test'}, :without_protection => true).save
For seed data, it may make sense to bypass validation which you can do like this:
Post.new({:id => 10, :title => 'Test'}, :without_protection => true).save(validate: false)
We've actually added a helper method to ActiveRecord::Base that is declared immediately prior to executing seed files:
class ActiveRecord::Base
def self.seed_create(attributes)
new(attributes, without_protection: true).save(validate: false)
end
end
And now:
Post.seed_create(:id => 10, :title => 'Test')
For Rails 4, you should be using StrongParams instead of protected attributes. If this is the case, you'll simply be able to assign and save without passing any flags to new:
Post.new(id: 10, title: 'Test').save # optionally pass `{validate: false}`
In Rails 4.2.1 with Postgresql 9.5.3, Post.create(:id => 10, :title => 'Test') works as long as there isn't a row with id = 10 already.
you can insert id by sql:
arr = record_line.strip.split(",")
sql = "insert into records(id, created_at, updated_at, count, type_id, cycle, date) values(#{arr[0]},#{arr[1]},#{arr[2]},#{arr[3]},#{arr[4]},#{arr[5]},#{arr[6]})"
ActiveRecord::Base.connection.execute sql