fredrikhenne/README.md

## README.md

      
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              README.md
            
          
    Rails Setting model

This is a semi-quick key/value store I put together for a quick way to store temporary data related to what's in my database, in a reliable way. For example, I'm using it to keep track of where a hourly and a daily crontask that processes statistics left off, so it can resume only processing and summarizing new data on the next run.
Code quality most likely is not great, but it works. And I will update this gist as I update my project.
How It Works

The settings table has two columns, a key and a value column. The value column is serialized, so you can technically store almost anything in there. Memcache is also used as a caching layer to minimize database calls.
Example usage

# fetching a value
>> Setting.hello
=> nil

# setting a value, writes it to memcache, and saves or updates a database
# record is the form of {:key => "hello", :value => serialize(["world"])}
>> Setting.hello = ["world"]
=> ["hello"]

# fetching the value again, which will only read from memcache
>> Setting.hello
=> ["hello"]

# force fetch from database and update memcache
>> Setting.hello!
=> ["hello"]

# remove the hello key from memcache and the database
>> Setting.hello = nil
=> nil

# default memcache expire_in option is 6.hours, you can change it...
>> Setting.__cache_expires_in = 1.hour
=> 3600 seconds


## create_settings.rb
class CreateSettings < ActiveRecord::Migration
  def self.up
    create_table :settings, :options => "ENGINE=InnoDB DEFAULT CHARSET=utf8" do |t|
      t.string :key
      t.text :value
    end

    add_index :settings, :key, :unique => true
  end

  def self.down
    drop_table :settings
  end
end

## setting.rb
class Setting < ActiveRecord::Base

  serialize :value

  class << self
    attr_accessor :__cache
    attr_accessor :__cache_expires_in
  end

  def self.method_missing(method, *args)

    # init memcache if needed
    @__cache = ActiveSupport::Cache::MemCacheStore.new if @__cache.nil?
    @__cache_expires_in = 6.hours if @__cache_expires_in.nil?

    method = method.to_s

    # set mode
    if method[-1,1] == "="

      if args.size > 0
        # key/value setup
        method = method.chop
        method = method.chop if method[-1,1] == "!"
        value = {:value => args[0]}
        @__cache.write(method, value, :expires_in => @__cache_expires_in)
        setting = self.find(:first, :conditions => {:key => method})
        if value[:value].nil?
          setting.destroy if setting
          @__cache.write(method, nil, :expires_in => 0.seconds)
        else
          setting = self.new if !setting
          setting.key = method.to_s if setting.key.blank?
          setting.value = value
          if setting.save
            return value[:value]
          end
        end
      end

    # get mode
    else

      # skip memcache?
      if method[-1,1] == "!"
        method = method.chop
        skip_cache = true
      end

      if skip_cache.nil? && (result = @__cache.read(method.to_s))
        return result[:value]
      else
        result = self.find(:first, :conditions => {:key => method})
        if result
          @__cache.write(method, result.value, :expires_in => @__cache_expires_in)
          return result.value[:value]
        end
      end

    end
    return nil

  end

end
	class CreateSettings < ActiveRecord::Migration
	def self.up
	create_table :settings, :options => "ENGINE=InnoDB DEFAULT CHARSET=utf8" do \|t\|
	t.string :key
	t.text :value
	end

	add_index :settings, :key, :unique => true
	end

	def self.down
	drop_table :settings
	end
	end
	class Setting < ActiveRecord::Base

	serialize :value

	class << self
	attr_accessor :__cache
	attr_accessor :__cache_expires_in
	end

	def self.method_missing(method, *args)

	# init memcache if needed
	@__cache = ActiveSupport::Cache::MemCacheStore.new if @__cache.nil?
	@__cache_expires_in = 6.hours if @__cache_expires_in.nil?

	method = method.to_s

	# set mode
	if method[-1,1] == "="

	if args.size > 0
	# key/value setup
	method = method.chop
	method = method.chop if method[-1,1] == "!"
	value = {:value => args[0]}
	@__cache.write(method, value, :expires_in => @__cache_expires_in)
	setting = self.find(:first, :conditions => {:key => method})
	if value[:value].nil?
	setting.destroy if setting
	@__cache.write(method, nil, :expires_in => 0.seconds)
	else
	setting = self.new if !setting
	setting.key = method.to_s if setting.key.blank?
	setting.value = value
	if setting.save
	return value[:value]
	end
	end
	end

	# get mode
	else

	# skip memcache?
	if method[-1,1] == "!"
	method = method.chop
	skip_cache = true
	end

	if skip_cache.nil? && (result = @__cache.read(method.to_s))
	return result[:value]
	else
	result = self.find(:first, :conditions => {:key => method})
	if result
	@__cache.write(method, result.value, :expires_in => @__cache_expires_in)
	return result.value[:value]
	end
	end

	end
	return nil

	end

	end