CODEWITHSUNDEEP
rubymongodbmongodb-query
dvxam
dvxam

Reputation: 604

Mongo, Ruby, Enumerable - What am i doing wrong?

What am I doing wrong?

db = Mongo::MongoClient.new(DB_URI)
tags = db['tags'].find()
tag_ids = tags.map { |t| t['_id'] }

puts tags.count
=> 4272

tags.each do |t|
  puts t.inspect
end
=> # does not produce anything. As if it was empty.

If i'm comment this line # tag_ids = tags.map { |t| t['_id'] }, the each method works correctly.

using ruby 1.9.3p545 and gem mongo 1.9.2

Upvotes: 0

Views: 69

Answers (1)

Neil Lunn
Neil Lunn

Reputation: 151122

The result of .find() is a cursor not an array or list. Cursors with databases only ever work one way and once only. You already pulled all the results out, so yes it is now empty when you go to use it again.

The .count() method returns meta-data from the cursor that holds the number returned. So usage of that is okay

You can use the .rewind() method. But all this really does is execute the query again. So that may or may not be what you want.

If you need to use the list several times, then pull all the results to their own array and do you different iterations that way. Or figure a way to do what you want in "one pass".

Upvotes: 2

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