Example of work with mongo

Rails
1

Hi there,
I’m newbie here and I have a problem with the connection with MongoDB.
The connection among Rails and MongoDB works, but I don’t know, how to
print only one “column” from document.
If I’m trying following a part of code:

puts db[“testCollection”].find_one().inspect

So I’will get the entire structure of BSON, as:

{"_id"=>#<BSON::ObjectID:0x118576c …>, “name”=>“MongoDB”,
“info”=>{“x”=>203, “y”=>102}, “type”=>“database”, “count”=>1}

But I would like to ask you, how is possible to get only the item eg
“name”… I am searching this information a long time, but no result
yet…

I will very glad for everything help, thanks a lot!

2

On Thu, Mar 3, 2011 at 4:41 PM, Manny 777 [email protected] wrote:

But I would like to ask you, how is possible to get only the item eg
“name”… I am searching this information a long time, but no result
yet…

db[“testCollection”].find_one[‘name’]

Hint: db["testCollection"].find_one.methods.sort will give you a lot
of useful information…

–
Hassan S. ------------------------ [email protected]
twitter: @hassan

3

Hi Hassan,
thanks for your reply.

This works, but if I am trying to select only one attribut from the
whole document,

db[“testCollection”].find[‘name’]

so that isn’t working. I must to type:

@array=db.collection(‘people’).find() #I’m selecting everything :confused:
i=0
for polozka in @array
puts “#{i}th item is: #{polozka[‘name’]}”
i+=1
end

Can you help with this? Thanks in advance!

4

On Fri, Mar 4, 2011 at 8:30 AM, Manny 777 [email protected] wrote:

This works, but if I am trying to select only one attribut from the
whole document,

I’m not sure if you’re trying to get only documents with a given name
or show the names of all documents, but have you gone through this:

http://api.mongodb.org/ruby/current/file.TUTORIAL.html

It will probably give you a good overall picture.

HTH!

Hassan S. ------------------------ [email protected]
twitter: @hassan

5

On Fri, Mar 4, 2011 at 10:30 AM, Manny 777 [email protected] wrote:

@array=db.collection(‘people’).find() #I’m selecting everything :confused:
i=0
for polozka in @array
puts “#{i}th item is: #{polozka[‘name’]}”
i+=1
end

Can you help with this? Thanks in advance!

I think you will find that this will work better. It will return an
array of
just the people’s names and then you can iterate over them.

arr_person = Person.find(:all).map {|p| p.name}
arr_person.each_with_index{|p,i| puts “#{i} has the name: #{p}”}

B.

6

On Fri, Mar 4, 2011 at 8:54 AM, Bryan C. [email protected]
wrote:

I think you will find that this will work better. It will return an array of
just the people’s names and then you can iterate over them.

arr_person = Person.find(:all).map {|p| p.name}

It would if the OP were using ActiveRecord with a Person object, but
the question is about MongoDB :slight_smile:

db.collection(‘people’).find().each_with_index { |x,y| puts “#{y}
#{x[‘name’]}” }

would actually work…

–
Hassan S. ------------------------ [email protected]
twitter: @hassan

7

Sample of Blog built with MongoDB http://rad-sample.heroku.com

8

Simple blog built with MongoDB http://rad-sample.heroku.com
sources https://github.com/alexeypetrushin/rad_sample

9

More examples:

Save any pure Ruby object (also complex & nested) in MongoDB
https://github.com/alexeypetrushin/mongo_db

  • driver API enhancements (100% backward-compatible with original API),
    makes API more friendly & handy, no extra abstraction or complexities
    introduced, all things are exactly the same as in MongoDB.

Sample:

class Unit
attr_reader :name

def initialize name = nil
  @name = name
end

end

zeratul = Unit.new ‘Zrtlu’ # wrong name
db.units.save zeratul

zeratul.name = ‘Zeratul’ # fixing name
db.units.save zeratul

db.units.first name: ‘Zeratul’ # => zeratul
db.units.by_name ‘Zeratul’ # => zeratul

And more