merge-mongoid

Easily merge two Mongoid documents.

What it does

Let's say we have two Mongo Documents : document A and document B (same class).

When merging document B into document A, arrays and nested objects will be merged, but duplicate values are not kept.

For the other data types we always keep Document A values, unless the A value is nil and the B is not.

Example of data merge

Object A :

{
	_id : "507f1f77bcf86cd799439011",
	a_string : "This is the A object"
    a_number : 100,
    a_boolean : true,
    array_simple_types : ["an","array","with","elements"],
    array_hashes : [{
      "id" : "507f191e810c19729de860ea",
      "attribute" : "yes there is one"
    },{
      "id" : "4f202e64e6fb1b56ff000000",
      "attribute" : "a value here too"
    }],
    a_hash : {
        "_id" : "5bf9f23d8ead0e1d32756346",
        "a string" : "hello",
        "a number" : 12
    }
}

Object B :

{
    _id : "4f2030d9e6fb1b56ff000001",
	a_string : "This is the B object"
    a_number : 8888,
    a_boolean : false,
    array_simple_types : ["an","array","with","cool","things"],
    array_hashes : [{
      "id" : "4af9f23d8ead0e1d32000000",
      "attribute" : "this is a different object"
    },{
      "id" : "4f202e64e6fb1b56ff000000",
      "attribute" : "this one was already there, but for some reason the attribute is different (which is weird BTW)"
    }],
    a_hash : {
        "_id" : "4af9f23d8ead0e1d32111111",
        "a string" : "another string value",
        "a number" : 40,
        "a third attribute" : true
    }
}

Ruby method call

A.merge! B

Now A contains these values :

{
	_id : "507f1f77bcf86cd799439011",
	a_string : "This is the A object"
    a_number : 100,
    a_boolean : true,
    array_simple_types : ["an","array","with","elements","cool","things"],
    array_hashes : [{
      "id" : "507f191e810c19729de860ea",
      "attribute" : "yes there is one"
    },{
      "id" : "4f202e64e6fb1b56ff000000",
      "attribute" : "a value here too"
    },{
      "id" : "4af9f23d8ead0e1d32000000",
      "attribute" : "this is a different object"
    }],
    a_hash : {
        "_id" : "5bf9f23d8ead0e1d32756346",
        "a string" : "hello",
        "a number" : 12,
        "a third attribute" : true
    }
}

Disclaimer

I am not a Ruby expert! I just happened to need this feature for a Rails app, so I developed a gem.

Probably a few things are not perfect or simply ARE NOT WHAT YOU WOULD EXPECT (ex : I don't keep duplicate values in arrays, but maybe you want to).

I highly recommend to test if the gem behaves correctly with your data before using it in production!

If you notice anything wrong, please feel free to send a Pull Request (including a fix + some tests). Same thing if you enhance the gem with some cool features, I would be happy to merge.

Getting Started

Install the gem with: gem install merge-mongoid or add gem 'merge-mongoid', :git => 'https://github.com/fallanic/merge-mongoid' to your Gemfile.

Usage

You need to add one line in your Model :

class Myclass
  include Mongoid::Document
  include Mongoid::Timestamps
  include Mongoid::Document::Mergeable
  
  ...
end

And then call :

A.merge! B

B attributes will be merged into A.

B is also destroyed after the merge has been successful.

Testing

In the terminal, you'll need to start a mongoDB connection

To do this, you'll need to run mongod while specifying a local folder

EX:

$ mkdir tmpdb
$ mongod --dbpath ./tmpdb

Open another tab and run rspec

That's all folks!

License

Copyright (c) 2013 Fabien Allanic
Licensed under the MIT license.