45 lines
911 B
Markdown
45 lines
911 B
Markdown
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---
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layout: post
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title: "Mongoid: Use ObjectId as created_at"
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date: 2013-08-23 07:34
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comments: true
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categories:
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- mongodb
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- rails
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- mongoid
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description: "Mongoid: Use ObjectId as created_at"
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---
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One great feature of Mongodb is, that the first bytes of each ObjectID contains the time, they were generated.
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This can be exploited to mimic the well known `created_at` field in rails.
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First put this file in your lib directory.
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```ruby
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#lib/mongoid/created.rb
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module Mongoid
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module CreatedAt
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# Returns the creation time calculated from ObjectID
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#
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# @return [ Date ] the creation time
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def created_at
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id.generation_time
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end
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end
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end
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```
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Now you can include this module in every Model, where you need created at.
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```ruby
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#app/models/user.rb
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class User
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include Mongoid::Document
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include Mongoid::CreatedAt
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# ...
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end
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u = User.new
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u.created_at
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```
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That's all easy enough, isn't it?
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