How to Get All Field Names of the Mongoid Document

How can I get all field names of the Mongoid Document?

Mongoid already provides you the attributes for an object:

Model.new.attributes

To get the names for these attributes:

Model.fields.keys

How get all column names of model in Mongoid

Use

Model.fields.keys

Replace Model with your model name

Listing fields in a mongodb object

MongoDB has a schema-less design, which means that any document could have different fields contained within it from any other document. To get an exhaustive list of all the fields for all the documents, you would need to traverse all the documents in the collection and enumerate each field. For any reasonably sized collection this is going to be an extremely expensive operation.

There are a couple of helpers that make this more simple: Variety and schema.js . They both allow you to limit the documents inspected, and they report on coverage as well. Both amount to doing a map/reduce on the collections, but are at least simpler than having to write one yourself.

Finding all documents in a collection with Mongoid

Category indeed doesn't have a method each because it's a model class, not a collection. It has, however, several methods that do return collection-like objects. One of them is all. So the code should look like this:

Category.all.each do |test|
  puts test.inspect
end

Get names of all keys in the collection

You could do this with MapReduce:

mr = db.runCommand({
  "mapreduce" : "my_collection",
  "map" : function() {
    for (var key in this) { emit(key, null); }
  },
  "reduce" : function(key, stuff) { return null; }, 
  "out": "my_collection" + "_keys"
})

Then run distinct on the resulting collection so as to find all the keys:

db[mr.result].distinct("_id")
["foo", "bar", "baz", "_id", ...]

Mongoid - getting all attributes including embedded documents

Since embedded documents are really just other attributes on the parent document, you can get to them like so:

person = Person.create
person.phone_numbers.create(:number => "123-456-7890")
person.attributes
# => {"_id"=>"4c48ff26f7e2da3704000001",
#    "phone_numbers"=>
#     [{"number"=>"123-456-7890", "_id"=>"4c48ff26f7e2da3704000002"}]}

Mongoid: find all children documents of multiple parent documents

You can use organization_id.in

@locations = Location.where(:organization_id.in => orgs.map(&:id))

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