In our Rails app environment (ruby 1.8.7 / rails 2.3.12) I can run the following code:
class MongoTester
include MongoMapper::Document
key :test_arr, Array, :default => []
end
mt = MongoTester.new
mt.test_arr << 24
mt2 = MongoTester.new
The output of mt2.inspect is:
#<MongoTester test_arr: [24], _id: BSON::ObjectId('4e5c089f3beaacad00000002')>
I'm not sure how this is possible. object_id and _id for both records are different. Neither one is saved. We haven't modified MongoMapper in our application (mongomapper 0.8.6). Yet a completely new record contains the data of a previously created different record.
I can't reproduce this in MongoMapper's test suite.
Any information on how this effect is possible or how I can get rid of it would be awesome. Thanks!
That is a bug: file it at https://github.com/jnunemaker/mongomapper/issues/new This bug is fixed in newer versions of MongoMapper
Here's a workaround:
key :test_arr, Array, :default => lambda { [] }
It's because arrays in Ruby are mutable, so your default array object is getting added to each time with <<. The object_id's of your docs will be different, but the object_id's of the arrays will be the same.
Related
I have a user model with a friends column of type text. This migration was ran to use the array feature with postgres:
add_column :users, :friends, :text, array: true
The user model has this method:
def add_friend(target)
#target would be a value like "1234"
self.friends = [] if self.friends == nil
update_attributes friends: self.friends.push(target)
end
The following spec passes until I add user.reload after calling #add_friend:
it "adds a friend to the list of friends" do
user = create(:user, friends: ["123","456"])
stranger = create(:user, uid: "789")
user.add_friend(stranger.uid)
user.reload #turns the spec red
user.friends.should include("789")
user.friends.should include("123")
end
This happens in development as well. The model instance is updated and has the new uid in the array, but once reloaded or reloading the user in a different action, it reverts to what it was before the add_friend method was called.
Using Rails 4.0.0.rc2 and pg 0.15.1
What could this be?
I suspect that ActiveRecord isn't noticing that your friends array has changed because, well, the underlying array reference doesn't change when you:
self.friends.push(target)
That will alter the contents of the array but the array itself will still be the same array. I know that this problem crops up with the postgres_ext gem in Rails3 and given this issue:
String attribute isn't marked as dirty, when it changes with <<
I'd expect Rails4 to behave the same way.
The solution would be to create a new array rather than trying to modify the array in-place:
update_attributes friends: self.friends + [ target ]
There are lots of ways to create a new array while adding an element to an existing array, use whichever one you like.
It looks like the issue might be your use of push, which modifies the array in place.
I can't find a more primary source atm but this post says:
One important thing to note when interacting with array (or other mutable values) on a model. ActiveRecord does not currently track "destructive", or in place changes. These include array pushing and poping, advance-ing DateTime objects. If you want to use a "destructive" update, you must call <attribute>_will_change! to let ActiveRecord know you changed that value.
If you want to use Postgresql array type, you'll have to comply with its format. From Postgresql docs the input format is
'{10000, 10000, 10000, 10000}'
which is not what friends.to_s will return. In ruby:
[1,2,3].to_s => "[1,2,3]"
That is, brackets instead of braces. You'll have to do the conversion yourself.
However I'd much rather rely on ActiveRecord serialize (see serialize). The database does not need to know that the value is actually an array, that's your domain model leaking into your database. Let Rails do its thing and encapsulate that information; it already knows how to serialize/deserialize the value.
Note: This response is applicable to Rails 3, not 4. I'll leave here in case it helps someone in the future.
I have a user model with a friends column of type text. This migration was ran to use the array feature with postgres:
add_column :users, :friends, :text, array: true
The user model has this method:
def add_friend(target)
#target would be a value like "1234"
self.friends = [] if self.friends == nil
update_attributes friends: self.friends.push(target)
end
The following spec passes until I add user.reload after calling #add_friend:
it "adds a friend to the list of friends" do
user = create(:user, friends: ["123","456"])
stranger = create(:user, uid: "789")
user.add_friend(stranger.uid)
user.reload #turns the spec red
user.friends.should include("789")
user.friends.should include("123")
end
This happens in development as well. The model instance is updated and has the new uid in the array, but once reloaded or reloading the user in a different action, it reverts to what it was before the add_friend method was called.
Using Rails 4.0.0.rc2 and pg 0.15.1
What could this be?
I suspect that ActiveRecord isn't noticing that your friends array has changed because, well, the underlying array reference doesn't change when you:
self.friends.push(target)
That will alter the contents of the array but the array itself will still be the same array. I know that this problem crops up with the postgres_ext gem in Rails3 and given this issue:
String attribute isn't marked as dirty, when it changes with <<
I'd expect Rails4 to behave the same way.
The solution would be to create a new array rather than trying to modify the array in-place:
update_attributes friends: self.friends + [ target ]
There are lots of ways to create a new array while adding an element to an existing array, use whichever one you like.
It looks like the issue might be your use of push, which modifies the array in place.
I can't find a more primary source atm but this post says:
One important thing to note when interacting with array (or other mutable values) on a model. ActiveRecord does not currently track "destructive", or in place changes. These include array pushing and poping, advance-ing DateTime objects. If you want to use a "destructive" update, you must call <attribute>_will_change! to let ActiveRecord know you changed that value.
If you want to use Postgresql array type, you'll have to comply with its format. From Postgresql docs the input format is
'{10000, 10000, 10000, 10000}'
which is not what friends.to_s will return. In ruby:
[1,2,3].to_s => "[1,2,3]"
That is, brackets instead of braces. You'll have to do the conversion yourself.
However I'd much rather rely on ActiveRecord serialize (see serialize). The database does not need to know that the value is actually an array, that's your domain model leaking into your database. Let Rails do its thing and encapsulate that information; it already knows how to serialize/deserialize the value.
Note: This response is applicable to Rails 3, not 4. I'll leave here in case it helps someone in the future.
I'm working with Rails 4.1.0, Ruby 2.1.0, and Postgres 9.3.0.0.
I'm trying to save changes to a column which is an array of hstores (an array of hashes in ruby parlance).
Here's the (simplified) code in the product model, used for saving the changes:
def add_to_cart_with_credits(cart)
cart.added_product_hashes << {"id" => self.id.to_s, "method" => "credits"}
# For some reason, this isn't saving (without the exclamation, as well)
cart.save!
end
A few things of note:
The cart is initialised with an empty array in the added_product_hashes column
I'm storing added products as hashes because there are a couple of ways to add products to the cart, and they each require their own logic to remove and customise.
Each user has their own cart, and needs to reference it later, which is why carts are saved to the DB like this (instead of using a session variable, I guess).
Any ideas what I'm doing wrong? I'm not seeing an error: the server logs note that the cart.added_product_hashes column updates correctly, but the changes don't persist.
SOLUTION
As James pointed out, << doesn't flag the record as being dirty, as it edits the array in-place. While I wasn't changing the hstores themselves within the array column, it appears that changes to the enclosing array aren't picked up unless the attribute is explicitly reconstructed. The below code fixes the problem:
def add_to_cart_with_credits(cart)
cart.added_product_hashes = cart.added_product_hashes + [{"id" => self.id.to_s, "method" => "credits"}]
# Now we're all good to go!
cart.save!
end
James also suggests a particular method that would be more terse.
See "New data not persisting to Rails array column on Postgres"
ActiveRecord isn't recognizing the change to the array as attributes are being updated in place.
You can also do something like this:
cart.added_product_hashes_will_change!
I have a user model with a friends column of type text. This migration was ran to use the array feature with postgres:
add_column :users, :friends, :text, array: true
The user model has this method:
def add_friend(target)
#target would be a value like "1234"
self.friends = [] if self.friends == nil
update_attributes friends: self.friends.push(target)
end
The following spec passes until I add user.reload after calling #add_friend:
it "adds a friend to the list of friends" do
user = create(:user, friends: ["123","456"])
stranger = create(:user, uid: "789")
user.add_friend(stranger.uid)
user.reload #turns the spec red
user.friends.should include("789")
user.friends.should include("123")
end
This happens in development as well. The model instance is updated and has the new uid in the array, but once reloaded or reloading the user in a different action, it reverts to what it was before the add_friend method was called.
Using Rails 4.0.0.rc2 and pg 0.15.1
What could this be?
I suspect that ActiveRecord isn't noticing that your friends array has changed because, well, the underlying array reference doesn't change when you:
self.friends.push(target)
That will alter the contents of the array but the array itself will still be the same array. I know that this problem crops up with the postgres_ext gem in Rails3 and given this issue:
String attribute isn't marked as dirty, when it changes with <<
I'd expect Rails4 to behave the same way.
The solution would be to create a new array rather than trying to modify the array in-place:
update_attributes friends: self.friends + [ target ]
There are lots of ways to create a new array while adding an element to an existing array, use whichever one you like.
It looks like the issue might be your use of push, which modifies the array in place.
I can't find a more primary source atm but this post says:
One important thing to note when interacting with array (or other mutable values) on a model. ActiveRecord does not currently track "destructive", or in place changes. These include array pushing and poping, advance-ing DateTime objects. If you want to use a "destructive" update, you must call <attribute>_will_change! to let ActiveRecord know you changed that value.
If you want to use Postgresql array type, you'll have to comply with its format. From Postgresql docs the input format is
'{10000, 10000, 10000, 10000}'
which is not what friends.to_s will return. In ruby:
[1,2,3].to_s => "[1,2,3]"
That is, brackets instead of braces. You'll have to do the conversion yourself.
However I'd much rather rely on ActiveRecord serialize (see serialize). The database does not need to know that the value is actually an array, that's your domain model leaking into your database. Let Rails do its thing and encapsulate that information; it already knows how to serialize/deserialize the value.
Note: This response is applicable to Rails 3, not 4. I'll leave here in case it helps someone in the future.
So I've done a couple of days worth of research on the matter, and the general consensus is that there isn't one. So I was hoping for an answer more specific to my situation...
I'm using Rails to import a file into a database. Everything is working regarding the import, but I'm wanting to give the database itself an attribute, not just every entry. I'm creating a hash of the file, and I figured it'd be easiest to just assign it to the database (or the class).
I've created a class called Issue (and thus an 'issues' database) with each entry having a couple of attributes. I was wanting to figure out a way to add a class variable (at least, that's what I think is the best option) to Issue to simply store the hash. I've written a rake to import the file, iff the new file is different than the previous file imported (read, if the hash's are different).
desc "Parses a CSV file into the 'issues' database"
task :issues, [:file] => :environment do |t, args|
md5 = Digest::MD5.hexdigest(args[:file])
puts "1: Issue.md5 = #{Issue.md5}"
if md5 != Issue.md5
Issue.destroy_all()
#import new csv file
CSV.foreach(args[:file]) do |row|
issue = {
#various attributes to be columns...
}
Issue.create(issue)
end #end foreach loop
Issue.md5 = md5
puts "2: Issue.md5 = #{Issue.md5}"
end #end if statement
end #end task
And my model is as follows:
class Issue < ActiveRecord::Base
attr_accessible :md5
##md5 = 5
def self.md5
##md5
end
def self.md5=(newmd5)
##md5 = newmd5
end
attr_accessible #various database-entry attributes
end
I've tried various different ways to write my model, but it all comes down to this. Whatever I set the ##md5 in my model, becomes a permanent change, almost like a constant. If I change this value here, and refresh my database, the change is noted immediately. If I go into rails console and do:
Issue.md5 # => 5
Issue.md5 = 123 # => 123
Issue.md5 # => 123
But this change isn't committed to anything. As soon as I exit the console, things return to "5" again. It's almost like I need a .save method for my class.
Also, in the rake file, you see I have two print statements, printing out Issue.md5 before and after the parse. The first prints out "5" and the second prints out the new, correct hash. So Ruby is recognizing the fact that I'm changing this variable, it's just never saved anywhere.
Ruby 1.9.3, Rails 3.2.6, SQLite3 3.6.20.
tl;dr I need a way to create a class variable, and be able to access it, modify it, and re-store it.
Fixes please? Thanks!
There are a couple solutions here. Essentially, you need to persist that one variable: Postgres provides a key/value store in the database, which would be most ideal, but you're using SQLite so that isn't an option for you. Instead, you'll probably need to use either redis or memcached to persist this information into your database.
Either one allows you to persist values into a schema-less datastore and query them again later. Redis has the advantage of being saved to disk, so if the server craps out on you you can get the value of md5 again when it restarts. Data saved into memcached is never persisted, so if the memcached instance goes away, when it comes back md5 will be 5 once again.
Both redis and memcached enjoy a lot of support in the Ruby community. It will complicate your stack slightly installing one, but I think it's the best solution available to you. That said, if you just can't use either one, you could also write the value of md5 to a temporary file on your server and access it again later. The issue there is that the value then won't be shared among all your server processes.