Module: Mongoid::TLL

Defined in:
lib/mongoid/tll.rb

Overview

Include this module to have documents automatically cloned when updated. It constructs a top linked list (like a doubly linked list with a pointer to the newest version) out of the chain of documents. Only use this when in 99% of the time only the newest version of a document is read! Mongoid::Versioning will take care of all the other usecases.

Class Method Summary collapse

Class Method Details

.included(klass) ⇒ Object 



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# File 'lib/mongoid/tll.rb', line 10

def self.included(klass)
  klass.class_exec do
    
    # The linked list pointers.
    field :tll_top
    field :tll_prev
    index :tll_top

    # By default, get the newest only.
    default_scope where: {tll_top: nil}
    
    set_callback :save, :before, :tll_commit
    attr_protected :tll_top, :tll_prev
    
    # Function that is called before saving a document.
    # It's responsible for the versioning.
    def tll_commit
      oldself = self.class.unscoped.where(_id: id).first
      if oldself # We've got a previous saved document.
        self.class.unscoped.where(tll_top: oldself._id)\
          .update_all(tll_top: id)
        oldself = oldself.clone
        oldself.tll_top = id
        self.tll_prev = oldself._id
        oldself.save
      end
    end
    
    # Is this the newest version?
    def newest?
      self.tll_top.nil?
    end
    
    # Return the newest version.
    def newest
      unless newest?
        return self.class.unscoped.where(_id: self.tll_top).first
      end

      self
    end
    
    # Is this the oldest version?
    def oldest?
      self.tll_prev.nil?
    end
    
    # Return the previous version, if there is any.
    # Will return nil when #oldest? is true.
    def prev
      unless self.tll_prev.nil?
        return self.class.unscoped.where(_id: self.tll_prev).first
      end

      nil
    end
  end
end