Class: ActiveMerge::Service

Inherits:
ActivePatterns::BaseService
  • Object
show all
Includes:
ActiveModel::Validations
Defined in:
lib/active_merge/service.rb

Overview

Service Object responds for merging given ActiveRecord instances into the first one

Object initializes either with ActiveRecord::Association or array of objects. If the argument is an array, then only those items taken into account, that:

  • inherited from the ActiveRecord::Base

  • persisted

  • are objects of one class

Merging algorithm

  • The item with minimal id selected from the service argument. It will remaine intact.

  • All objects, that the other items links to via “has_many” assotiation, are selected…

  • … and are rebound to the first item

  • After rebinding any item from the service argument, except the first one, to be deleted.

As a result it is only the first object from the argument remains intact, and all the instances that belonged to the other ones are now belongs to it.

Example:

# Let any kingdom has many shires and men
class Kingdom < ActiveRecord::Base
  has_many :shires
  has_many :men
end

class Shire < ActiveRecord::Base
  belongs_to :kingdom
end

class Man < ActiveRecord::Base
  belongs_to :kingdom
end

# Britain has 10 shires and 100 thousands men lives there
britain  = Kingdom.create!
100000.times.each{ britain.men.create! }
10.times.each{ britain.shires.create! }

# Scotland has 5 shires and 30 thousands living men
scotland = Kingdom.create!
30000.times.each{ scotland.men.create! }
5.times.each{ scotland.shires.create! }

# Lets merge all the kingdoms:
Service.new(Kingdom.all).submit!

# Now union Britain (because it is Britain that was created first) 
# has all those 15 shires and 130 thousand men
# from both the old good Britain and the old good Scotland.
britain.reload.men.count # => 130000
britain.reload.shires.count # => 15

# And, alas, the Scotland Kingdom doesn't exists any more
Kingdom.find_by(scotland.id)  # => nil

Warning!

The merge provided as a whole transaction. In case any error occures, all the changes rolled back.

Let (see the example above) the shire cannot be rebount to another kingdom:

class Shire
  attr_readonly :kingdom_id
end

then merging won’t be finished.

Not only shires, but also the scots remain living in their Scotland, not in the United Kingdom!

Defined Under Namespace

Classes: Item, Items

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(list = nil) ⇒ Service 



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# File 'lib/active_merge/service.rb', line 81

def initialize(list = nil)
  list = Items.new list
  @item, @items = list.first, Array(list[1..-1])
end

Instance Attribute Details

#item ⇒ Object (readonly)

Returns the value of attribute item.



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# File 'lib/active_merge/service.rb', line 86

def item
  @item
end

#items ⇒ Object (readonly)

Returns the value of attribute items.



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# File 'lib/active_merge/service.rb', line 86

def items
  @items
end

#klass ⇒ Object (readonly)

Returns the value of attribute klass.



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# File 'lib/active_merge/service.rb', line 86

def klass
  @klass
end

#klasses ⇒ Object (readonly)

Returns the value of attribute klasses.



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# File 'lib/active_merge/service.rb', line 86

def klasses
  @klasses
end

Instance Method Details

#provide ⇒ Object

Merges all the #items to the #item as a whole transaction



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# File 'lib/active_merge/service.rb', line 90

def provide
  transaction do
    items.each do |item|
      service = SimpleService.new(self.item, item)
      change(service) { service.provide }
    end
  end
end