I'm using MongoDB but I'm not really using it's dynamic fields capabilities
field :fb_followers => Integer
field :twitter_followers => Integer
field :twitter_rts => Integer
field :link_visiting => Integer
field :reduce_points_per_day => Integer
How do I write this so each of those fields is optional for the model?
So here's some Mongoid-specific information. First of all, make sure allow_dynamic_fields is set to true in your configuration (it defaults to true, but always good to be sure).
Here's the world's simplest Mongoid class, for my examples:
class Foobj
include Mongoid::Document
field :static_field
end
So, we can of course set our static_field normally:
ruby-1.9.2-p290 :012 > f = Foobj.create!(:static_field => 'barbaz!')
=> #<Foobj _id: 4ec1f2eb90a110143b000003, _type: nil, regular_field: nil, static_field: "barbaz!">
But we can't do a dynamic field "on the fly" because Mongoid doesn't know about it yet.
ruby-1.9.2-p290 :013 > f.dynamic_field = "hi"
NoMethodError: undefined method `dynamic_field=' for #<Foobj:0x000000044e7ee8>
However, I can use write_attribute to write a dynamic field:
ruby-1.9.2-p290 :014 > f.write_attribute(:dynamic_field,"hi!")
=> "hi!"
ruby-1.9.2-p290 :015 > f
=> #<Foobj _id: 4ec1f2eb90a110143b000003, _type: nil, regular_field: nil, static_field: "barbaz!", dynamic_field: "hi!">
And, now that I've "created" that field in Mongoid, I can now use the regular mechanism for accessing a field, even though it's not in my class definition:
ruby-1.9.2-p290 :017 > f.dynamic_field
=> "hi!"
Also, note that if you load a Mongoid document with non-Mongoid-specified fields, you can indeed access them the same way:
ruby-1.9.2-p290 :028 > g = Foobj.first
=> #<Foobj _id: 4ec1f2eb90a110143b000003, _type: nil, regular_field: nil, dynamic_field: "hi!", static_field: "barbaz!">
ruby-1.9.2-p290 :029 > g.dynamic_field
=> "hi!"
However, the safest way to work with dynamic fields is using write_attribute and read_attribute (or their shortcuts, []= and []) as these won't throw NoMethodErrors if the field doesn't exist.
Hope that helps. It's really pretty simple when you get used to it. For more info, see: http://mongoid.org/docs/documents/dynamic.html
As @rubish said all fields in MongoDB except _id are optional in MongoDB (unless you are using a capped collection in which case all are optional).
To save a record such as this without those fields you can do:
insert({ "some_field_not_related_to_others": 456 })
Then to save a record with those fields (does not need to be all of them can be a selection of fields):
insert({ "fb_followers": 1, "twitter_follower": 2, "twitter_rts": 5 //etc })
MongoDB will save the record in whatever format you provide in the insert statement since it is schemaless (more information can be found here: http://en.wikipedia.org/wiki/NoSQL).
It means every row is independant of the one above and of any standardised nessecarity to carry a certain amount of rows or fields.
As such to "define them optional" you merely do not insert them.
If this does not answer the quesiton maybe you can be more specific on which side you mean "optional" since I noticed this is a ruby question so you might be looking to make it optional in there rather than mark it as optional in the DB.
Just some playing around in the console to illustrate what I meant by "They are optional until you write some validation to check their presence.":
class Stat
include Mongoid::Document
field :fb_followers, :type => Integer
field :twitter_followers, :type => Integer
field :twitter_rts, :type => Integer
field :link_visiting, :type => Integer
field :reduce_points_per_day, :type => Integer
end
pry(main)> Stat.create(:fb_followers => 15).as_document
#=> {"fb_followers"=>15, "_id"=>BSON::ObjectId('4ec1ff1a75f38e676400000d')}
pry(main)> Stat.create(:fb_followers => 15, :twitter_rts => 30).as_document
#=> {"fb_followers"=>15, "twitter_rts"=>30, "_id"=>BSON::ObjectId('4ec1ff2b75f38e676400000e')}
pry(main)> Stat.create(:fb_followers => 15, :twitter_followers => 30).as_document
#=> {"fb_followers"=>15, "twitter_followers"=>30, "_id"=>BSON::ObjectId('4ec1ff4775f38e676400000f')}
Mongodb documments mostly look like output of as_document. Keys for which no value is set are not set, do not get set in mongodb. I hope that answers the question.
class Foo
include Mongoid::Document
field :abc, :type => Integer
end
If you want add one more field :xyz dynamically then you can use syntax below.
irb(main):005:0> foo = Foo.new
irb(main):006:0> foo.abc = 1
irb(main):009:0> foo["xyz"] = 2 #dynamic field
irb(main):010:0> foo
=> #<Foo _id: 51f23eebd1d872be84000001, abc: 1, xyz: 2>
