Rails model Serialization Hi Friends,
Earlier we have discussed about Association in Rails Model. Today we will be covering one more topic related to rails active records, that is Serialization. In summary we can define serialized objects as, So serialized objects (in the context of ActiveRecord) are text/string representations of objects. When serialized, you can save (almost) any Ruby object in a single database field.
In rails Serialization is done using ActiveModel::Serialization. It does a basic serialization of your object. But first you need to declare attribute hash with the attribute, you wish to serialize. It is must that these attributes are strings. You can represent this in Rails as:

class Blog
  include ActiveModel::Serialization
 
  attr_accessor :title

  def attributes
    {'title' => nil}
  end
end

For accessing serialized object, rails provide serializable_hash method.

blog = Blog.new
blog.serializable_hash   # => {"title"=>nil}
blog.title = "Association in Rails"
blog.serializable_hash   # => {"title"=>"Association in Rails"}

Rails provides two serializers for serialization, that are ActiveModel::Serializers::JSON and ActiveModel::Serializers::Xml. The use of these two in a Blog class will be like:

#For JSON
class Blog
  include ActiveModel::Serializers::JSON

  attr_accessor :title
 
  def attributes
    {'title' => nil}
  end
end


#For JSON
class Blog
  include ActiveModel::Serializers::Xml

  attr_accessor :title
 
  def attributes
    {'title' => nil}
  end
end

JSON and XML representation of models can be achieved using as_json and to_xml.eg:

#JSON
blog = Blog.new
blog.as_json # => {"title"=>nil}
blog.title = "Association in Rails"
blog.as_json # => {"title"=>"Association in Rails"}

#XML
blog = Blog.new
blog.to_xml # => "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<blog>\n  <title nil=\"true\"/>\n</blog>\n"
blog.title = "Association in Rails"
blog.to_xml # => "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<blog>\n  <title>Association in Rails</title>\n</blog>\n"

From both JSON and XML string as you define attributes, The method attributes= is used. As:

class Blog
  include ActiveModel::Serializers::JSON #Will be Xml in case of XML
 
  attr_accessor :title
 
  def attributes=(hash)
    hash.each do |key, value|
      send("#{key}=", value)
    end
  end
 
  def attributes
    {'title' => nil}
  end
end

At last creating instance of blog and setting value can be done using from_json and from_xml respectively. Example is given below:

#JSON:
json = { title: 'Association in Rails' }.to_json
blog = Blog.new
blog.from_json(json) # => #<Blog:0x00005c786391290 @title="Association in Rails">
blog.title           # => "Association in Rails"


#Similarly for XML:
xml = { title: 'Association in Rails' }.to_xml
blog = Blog.new
blog.from_xml(xml) # => #<Blog:0x00005c786391290 @title="Association in Rails">
blog.title         # => "Association in Rails"

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